feat(update): large update with new types, fixed bugs

build.gradle.kts

@@ -4,7 +4,7 @@ plugins {
 }
 
 group = "org.kargs"
-version = "1.0.0"
+version = "1.0.2"
 
 repositories {
     mavenCentral()
@@ -13,7 +13,27 @@ repositories {
 dependencies {
     testImplementation(kotlin("test"))
     implementation(kotlin("stdlib"))
-    implementation("org.jetbrains.kotlin:kotlin-reflect:2.2.21")
+    implementation(kotlin("reflect"))
+
+    // JUnit 5 testing dependencies
+    testImplementation("org.junit.jupiter:junit-jupiter-api:5.10.0")
+    testImplementation("org.junit.jupiter:junit-jupiter-engine:5.10.0")
+    testImplementation("org.junit.jupiter:junit-jupiter-params:5.10.0")
+    testImplementation(kotlin("test"))
+    
+    // For assertions
+    testImplementation("org.assertj:assertj-core:3.24.2")
+}
+
+tasks.test {
+    useJUnitPlatform()
+    
+    testLogging {
+        events("passed", "skipped", "failed")
+        showStandardStreams = true
+        exceptionFormat = org.gradle.api.tasks.testing.logging.TestExceptionFormat.FULL
+    }
+ 
 }
 
 mavenPublishing {

settings.gradle

@@ -1 +1 @@
-rootProject.name = "karg"
+rootProject.name = "kargs"

src/main/kotlin/org/kargs/ArgType.kt

@@ -1,23 +1,94 @@
 package org.kargs
 
+/**
+ * Sealed class representing different argument types with conversion and validation logic
+ */
 sealed class ArgType<T>(val typeName: String) {
+    /**
+     * Convert a string value to the target type
+     * @throws ArgumentParseException if conversion fails
+     */
     abstract fun convert(value: String): T
 
+    /**
+     * Validate that a value is acceptable for this type
+     * @return true if valid, false otherwise
+     */
+    open fun validate(value: T): Boolean = true
+
+    /**
+     * Get a description of valid values for this type
+     */
+    open fun getValidationDescription(): String = "any $typeName"
+
     object StringType : ArgType<kotlin.String>("String") {
         override fun convert(value: String) = value
     }
 
     object IntType : ArgType<kotlin.Int>("Int") {
-        override fun convert(value: String) = value.toInt()
+        override fun convert(value: String): kotlin.Int = value.toIntOrNull() ?: throw ArgumentParseException("`$value` is not a valid integer")
     }
 
     object BooleanType : ArgType<kotlin.Boolean>("Boolean") {
-        override fun convert(value: String) = value.toBoolean()
+        override fun convert(value: String): kotlin.Boolean {
+            return when (value.lowercase()) {
+                "true", "yes", "1", "on" -> true
+                "false", "no", "0", "off" -> false
+                else -> throw ArgumentParseException("'$value' is not a valid boolean (true/false, yes/no, 1/0, on/off)")
+            }
+        }
+    }
+
+    object DoubleType : ArgType<kotlin.Double>("Double") {
+        override fun convert(value: String): kotlin.Double {
+            return value.toDoubleOrNull()
+                ?: throw ArgumentParseException("'$value' is not a valid number")
+        }
+    }
+
+    /**
+     * Create a constrained integer type with min/max bounds
+     */
+    class IntRange(private val min: kotlin.Int, private val max: kotlin.Int) : ArgType<kotlin.Int>("Int") {
+        override fun convert(value: String): kotlin.Int {
+            val intValue = value.toIntOrNull() ?: throw ArgumentParseException("`$value` is not a valid integer")
+            if (intValue !in min..max) {
+                throw ArgumentParseException("`$value` must be between $min and $max")
+            }
+            return intValue
+        }
+
+        override fun getValidationDescription(): String = "integer between $min and $max"
+    }
+
+    /**
+     * Create an enum type from list of valid choices
+     */
+    class Choice(private val choices: List<kotlin.String>) : ArgType<kotlin.String>("Choice") {
+        override fun convert(value: String): kotlin.String {
+            if (value !in choices) {
+                throw ArgumentParseException("`$value` is not a valid choice. Valid options: ${choices.joinToString(", ")}")
+            }
+            return value
+        }
+
+        override fun getValidationDescription(): String = "one of: ${choices.joinToString(", ")}"
     }
 
     companion object {
         val String: ArgType<kotlin.String> = StringType
         val Int: ArgType<kotlin.Int> = IntType
         val Boolean: ArgType<kotlin.Boolean> = BooleanType
+        val Double: ArgType<kotlin.Double> = DoubleType
+
+        /**
+         * Create an integer type with bounds
+         */
+        fun intRange(min: kotlin.Int, max: kotlin.Int) = IntRange(min, max)
+
+        /**
+         * Create a choice type from valid options
+         */
+        fun choice(vararg options: kotlin.String) = Choice(options.toList())
     }
 }

src/main/kotlin/org/kargs/Argument.kt

@@ -1,26 +1,40 @@
 package org.kargs
 
-import kotlin.properties.ReadWriteProperty
-import kotlin.reflect.KProperty
-
+/**
+ * Represents a positional command-line argument
+ *
+ * @param type The type converter for this argument's value
+ * @param name The name of this argument (used in help)
+ * @param description Help text for this argument
+ * @param required Whether this argument must be provided
+ */
 class Argument<T>(
     val type: ArgType<T>,
     val name: String,
-    val description: String = "",
+    description: String? = null,
     val required: Boolean = true
-) : ReadWriteProperty<Any?, T?> {
+) : KargsProperty<T>(description) {
+    init {
+        require(name.isNotBlank()) { "Argument name cannot be blank" }
+    }
 
-    private var _value: T? = null
+    override fun parseValue(str: String) {
+        value = type.convert(str)
+    }
 
-    var value: T?
-    get() = _value
-    set(v) { _value = v }
+    override fun isValid(): Boolean {
+        return if (required) {
+            value != null && type.validate(value!!)
+        } else {
+            value?.let { type.validate(it) } ?: true
+        }
+    }
 
-    override fun getValue(thisRef: Any?, property: KProperty<*>): T? = _value
-    override fun setValue(thisRef: Any?, property: KProperty<*>, value: T?) { _value = value }
-
-    fun parseValue(input: String) {
-        _value = type.convert(input)
+    override fun getValidationError(): String? {
+        return when {
+            required && value == null -> "Argument '$name' is required"
+            value != null && !type.validate(value!!) -> "Invalid value for argument '$name': expected ${type.getValidationDescription()}"
+            else -> null
+        }
     }
 }
-

src/main/kotlin/org/kargs/Flag.kt

@@ -1,24 +1,53 @@
 package org.kargs
 
-import kotlin.properties.ReadWriteProperty
-import kotlin.reflect.KProperty
-
+/**
+ * Represents a boolean flag that doesn't take a value (e.g. --verbose, -v)
+ *
+ * @param longName The long form name (used with --)
+ * @param shortName The short form name (used with -)
+ * @param description Help text for this flag
+ * @param defaultValue Default value (typically false)
+ */
 class Flag(
     val longName: String,
     val shortName: String? = null,
-    val description: String = "",
-    val default: Boolean = false
-) : ReadWriteProperty<Any?, Boolean> {
+    description: String? = null,
+    private val defaultValue: Boolean = false,
+) : KargsProperty<Boolean>(description) {
 
-    private var _value = default
+    private var wasExplicitlySet = false
 
-    var value: Boolean
-    get() = _value
-    set(v) { _value = v }
+    init {
+        value = defaultValue
 
-    override fun getValue(thisRef: Any?, property: KProperty<*>): Boolean = _value
-    override fun setValue(thisRef: Any?, property: KProperty<*>, value: Boolean) { _value = value }
+        // Validate names
+        require(longName.isNotBlank()) { "Long name cannot be blank" }
+        require(!longName.startsWith("-")) { "Long name should not start with dashes" }
+        shortName?.let {
+            require(it.length == 1) { "Short name must be exactly one character" }
+            require(!it.startsWith("-")) { "Short name should not start with dashes" }
+        }
+    }
 
-    fun setFlag() { _value = true }
+    override fun parseValue(str: String) {
+        value = when (str.lowercase()) {
+            "true", "yes", "1", "on" -> true
+            "false", "no", "0", "off" -> false
+            else -> throw ArgumentParseException("Invalid flag value: $str")
+        }
+        wasExplicitlySet = true
+    }
+
+    /**
+     * Set the flag to true (called when flag is present)
+     */
+    fun setFlag() {
+        value = true
+        wasExplicitlySet = true
+    }
+
+    /**
+     * Check if this flag was explicitly set
+     */
+    fun isSet(): Boolean = wasExplicitlySet
 }
-

src/main/kotlin/org/kargs/KargsProperty.kt

@@ -0,0 +1,51 @@
+package org.kargs
+
+import kotlin.reflect.KProperty
+
+/**
+ * Base class for all command-line argument properties (options, flags, arguments)
+ */
+abstract class KargsProperty<T>(val description: String? = null) {
+    var value: T? = null
+        protected set
+    
+    internal lateinit var parent: Subcommand
+
+    /**
+     * Parse a string value into the appropiate type
+     * @throws ArgumentParseException if parsing fails
+     */
+    abstract fun parseValue(str: String)
+
+    /**
+     * Validate the current value
+     * @return true if valid, false otherwise
+     */
+    open fun isValid(): Boolean = true
+
+    /**
+     * Get validation error message if value is invalid
+     */
+    open fun getValidationError(): String? = null
+
+    /**
+     * Property delagate setup - registers this property with its parent subcommand
+     */
+    operator fun provideDelegate(thisRef: Subcommand, prop: KProperty<*>): KargsProperty<T> {
+        parent = thisRef
+        parent.registerProperty(this)
+        return this
+    }
+
+    /**
+     * Property delagate getter
+     */
+    operator fun getValue(thisRef: Subcommand, property: KProperty<*>): T? = value
+
+    /*
+     * Property delagate setter
+     */
+    operator fun setValue(thisRef: Subcommand, property: KProperty<*>, value: T?) {
+        this.value = value
+    }
+}

src/main/kotlin/org/kargs/Option.kt

@@ -1,28 +1,67 @@
 package org.kargs
 
-import kotlin.properties.ReadWriteProperty
-import kotlin.reflect.KProperty
-
+/**
+ * Represents a command-line option that takes a value (e.g. --output file.txt)
+ *
+ * @param type The type converter for this options's value
+ * @param longName The long form name (used with --)
+ * @param shortName The short form name (used with -)
+ * @param description Help text for this option
+ * @param required Whether this option must be provided
+ * @param defaultValue Default value if not provided
+ */
 class Option<T>(
     val type: ArgType<T>,
     val longName: String,
     val shortName: String? = null,
-    val description: String = "",
+    description: String? = null,
     val required: Boolean = false,
-    val default: T? = null
-) : ReadWriteProperty<Any?, T?> {
+    private val defaultValue: T? = null
+) : KargsProperty<T>(description) {
 
-    private var _value: T? = default
+    private var wasExplicitlySet = false
 
-    var value: T?
-    get() = _value
-    set(v) { _value = v }
+    init {
+        // Set the default value if provided
+        defaultValue?.let { value = it }
 
-    override fun getValue(thisRef: Any?, property: KProperty<*>): T? = _value
-    override fun setValue(thisRef: Any?, property: KProperty<*>, value: T?) { _value = value }
-
-    fun parseValue(input: String) {
-        _value = type.convert(input)
+        // Validate names
+        require(longName.isNotBlank()) { "Long name cannot be blank" }
+        require(!longName.startsWith("-")) { "Long name should not start with dashes" }
+        shortName?.let { 
+            require(it.length == 1) { "Short name must be exactly one character" }
+            require(!it.startsWith("-")) { "Short name should not start with dashes" }
+        }
     }
-}
 
+    override fun parseValue(str: String) {
+        value = type.convert(str)
+        wasExplicitlySet = true
+    }
+
+    override fun isValid(): Boolean {
+        return if (required) {
+            value != null && type.validate(value!!)
+        } else {
+            value?.let { type.validate(it) } ?: true
+        }
+    }
+
+    override fun getValidationError(): String? {
+        return when {
+            required && value == null -> "Option --$longName is required"
+            value != null && !type.validate(value!!) -> "Invalid value for --$longName: expected ${type.getValidationDescription()}"
+            else -> null
+        }
+    }
+
+    /**
+     * Check if the option has been set (different from default)
+     */
+    fun isSet(): Boolean = wasExplicitlySet
+
+    /**
+     * Get the value or default
+     */
+    fun getValueOrDefault(): T? = value ?: defaultValue
+}

src/main/kotlin/org/kargs/Parser.kt

@@ -1,98 +1,292 @@
 package org.kargs
 
-class Parser(val programName: String) {
+/**
+ * Main argument parser that handles command-line argument parsing and routing to subcommands.
+ *
+ * @param programName The name of the program (used in help messages)
+ * @param config Configuration options for the parser behavior
+ */
+class Parser(
+    val programName: String,
+    private val config: ParserConfig = ParserConfig.DEFAULT
+) {
     private val commands = mutableListOf<Subcommand>()
 
+    /**
+     * Register one or more subcommands with this parser
+     */
     fun subcommands(vararg cmds: Subcommand) {
         commands.addAll(cmds)
     }
 
+    /**
+     * Parse the provided command-line arguments and execute the appropiate command
+     *
+     * @param args Array of command-line arguments
+     */
     fun parse(args: Array<String>) {
         if (args.isEmpty()) {
+            if (config.helpOnEmpty) {
+                printGlobalHelp()
+            }
+            return
+        }
+
+        // Check for global help
+        if (args.contains("--help") || args.contains("-h")) {
             printGlobalHelp()
             return
         }
 
         val cmdName = args[0]
-        val cmd = commands.firstOrNull { it.name == cmdName || it.aliases.contains(cmdName) }
+        val cmd = findCommand(cmdName)
 
         if (cmd == null) {
-            println("Unknown command: $cmdName")
-            printGlobalHelp()
+            printError("Unknown command: $cmdName")
+            if (!config.strictMode) {
+                printGlobalHelp()
+            }
             return
         }
 
+        // Check for command specific help
         if (args.contains("--help") || args.contains("-h")) {
             cmd.printHelp()
             return
         }
 
-        // Reflection: find all Option, Flag, Argument properties
-        val props = cmd::class.members.filterIsInstance<kotlin.reflect.KProperty<*>>()
-        val options = props.mapNotNull { it.getter.call(cmd) as? Option<*> }
-        val flags = props.mapNotNull { it.getter.call(cmd) as? Flag }
-        val arguments = props.mapNotNull { it.getter.call(cmd) as? Argument<*> }
+        try {
+            parseCommandArgs(cmd, args.sliceArray(1 until args.size))
+            validateRequiredOptions(cmd)
+            cmd.execute()
+        } catch (e: ArgumentParseException) {
+            printError(e.message ?: "Parse error")
+            cmd.printHelp()
+            throw e
+        }
+    }
+
+    /**
+     * Find a command by name or alias
+     */
+    private fun findCommand(name: String): Subcommand? {
+        val searchName = if (config.caseSensitive) name else name.lowercase()
+        return commands.firstOrNull { cmd -> 
+            val cmdName = if (config.caseSensitive) cmd.name else cmd.name.lowercase()
+            val aliases = if (config.caseSensitive) cmd.aliases else cmd.aliases.map { it.lowercase() }
+            cmdName == searchName || aliases.contains(searchName)
+        }
+    }
+
+    /**
+     * Parse arguments for a specific command
+     */
+    private fun parseCommandArgs(cmd: Subcommand, args: Array<String>) {
+        var i = 0
+        val positionalArgs = mutableListOf<String>()
 
-        // Parse args starting at index 1
-        var i = 1
         while (i < args.size) {
             val arg = args[i]
+
             when {
                 arg.startsWith("--") -> {
                     val key = arg.removePrefix("--")
-                    val option = options.firstOrNull { it.longName == key }
-                    val flag = flags.firstOrNull { it.longName == key }
-
-                    when {
-                        option != null -> {
-                            i++
-                            if (i >= args.size) throw IllegalArgumentException("Missing value for option --$key")
-                            option.parseValue(args[i])
-                        }
-                        flag != null -> flag.setFlag()
-                        else -> println("Unknown option --$key")
-                    }
+                    i = parseLongOption(cmd, key, args, i)
                 }
 
-                arg.startsWith("-") -> {
+                arg.startsWith("-") && arg.length > 1 -> {
                     val key = arg.removePrefix("-")
-                    val option = options.firstOrNull { it.shortName == key }
-                    val flag = flags.firstOrNull { it.shortName == key }
-
-                    when {
-                        option != null -> {
-                            i++
-                            if (i >= args.size) throw IllegalArgumentException("Missing value for option -$key")
-                            option.parseValue(args[i])
-                        }
-                        flag != null -> flag.setFlag()
-                        else -> println("Unknown option -$key")
-                    }
+                    i = parseShortOption(cmd, key, args, i)
                 }
 
                 else -> {
-                    // Positional arguments
-                    val nextArg = arguments.firstOrNull { it.value == null }
-                    if (nextArg != null) {
-                        nextArg.parseValue(arg)
-                    } else {
-                        println("Unexpected argument: $arg")
-                    }
+                    positionalArgs.add(arg)
                 }
             }
             i++
         }
-
-        // Execute the command
-        cmd.execute()
+        // Handle positional arguments
+        parsePositionalArguments(cmd, positionalArgs)
     }
 
-    private fun printGlobalHelp() {
-        println("Usage: $programName <command> [options]")
-        println("\nCommands:")
-        commands.forEach {
-            println("  ${it.name}\t${it.description}")
+    /**
+     * Parse a long option (--option)
+     */
+    private fun parseLongOption(cmd: Subcommand, key: String, args: Array<String>, index: Int): Int {
+        val option = cmd.options.firstOrNull { it.longName == key }
+        val flag = cmd.flags.firstOrNull { it.longName == key }
+
+        return when {
+            option != null -> {
+                if (index + 1 >= args.size) {
+                    throw ArgumentParseException("Missing value for option --$key")
+                }
+                try {
+                    option.parseValue(args[index + 1])
+                    index + 1
+                } catch (e: Exception) {
+                    throw ArgumentParseException("Invalid value for option --$key: ${e.message}")
+                }
+            }
+
+            flag != null -> {
+                flag.setFlag()
+                index
+            }
+
+            else -> {
+                if (config.strictMode) {
+                    throw ArgumentParseException("Unknown option --$key")
+                } else {
+                    printWarning("Unknown option --$key")
+                    index
+                }
+            }
         }
     }
+
+    /**
+     * Parse a short option (-o)
+     */
+    private fun parseShortOption(cmd: Subcommand, key: String, args: Array<String>, index: Int): Int {
+        // Handle combined short flags like -acc
+        if (key.length > 1) {
+            key.forEach { char -> 
+                val flag = cmd.flags.firstOrNull { it.shortName == char.toString() }
+                if (flag != null) {
+                    flag.setFlag()
+                } else if (config.strictMode) {
+                    throw ArgumentParseException("Unknown flag -$char")
+                }
+            }
+            return index
+        }
+
+        val option = cmd.options.firstOrNull { it.shortName == key }
+        val flag = cmd.flags.firstOrNull { it.shortName == key }
+
+        return when {
+            option != null -> {
+                if (index + 1 >= args.size) {
+                    throw ArgumentParseException("Missing value for option -$key")
+                }
+                try {
+                    option.parseValue(args[index + 1])
+                    index + 1
+                } catch (e: Exception) {
+                    throw ArgumentParseException("Invalid value for option -$key: ${e.message}")
+                }
+            }
+
+            flag != null -> {
+                flag.setFlag()
+                index
+            }
+
+            else -> {
+                if (config.strictMode) {
+                    throw ArgumentParseException("Unknown option -$key")
+                } else {
+                    printWarning("Unknown option -$key")
+                    index
+                }
+            }
+        }
+    }
+
+    /**
+     * Parse positional arguments
+     */
+    private fun parsePositionalArguments(cmd: Subcommand, args: List<String>) {
+        val arguments = cmd.arguments
+
+        if (args.size > arguments.size) {
+            val extra = args.drop(arguments.size)
+            if (config.strictMode) {
+                throw ArgumentParseException("Too many arguments: ${extra.joinToString(", ")}")
+            } else {
+                printWarning("Ignoring extra arguments: ${extra.joinToString(", ")}")
+            }
+        }
+
+        args.forEachIndexed { index, value -> 
+            if (index < arguments.size) {
+                try {
+                    arguments[index].parseValue(value)
+                } catch (e: Exception) {
+                    throw ArgumentParseException("Invalid value for argument ${arguments[index].name}: ${e.message}")
+                }
+            }
+        }
+    }
+
+    /**
+     * Validate that all required options have been provided
+     */
+    private fun validateRequiredOptions(cmd: Subcommand) {
+        val missingRequired = cmd.options.filter { it.required && it.value == null }
+        if (missingRequired.isNotEmpty()) {
+            val missing = missingRequired.joinToString(", ") { "--${it.longName}" }
+            throw ArgumentParseException("Missing required options: $missing")
+        }
+    }
+
+    /**
+     * Print global help menu
+     */
+    private fun printGlobalHelp() {
+        println(colorize("Usage: $programName <command> [options]", Color.BOLD))
+        println()
+        println(colorize("Commands:", Color.BOLD))
+        commands.forEach { cmd -> 
+            val aliases = if (cmd.aliases.isNotEmpty()) " (${cmd.aliases.joinToString(", ")})" else ""
+            println("  ${colorize(cmd.name, Color.GREEN)}$aliases")
+            if (cmd.description.isNotEmpty()) {
+                println("    ${cmd.description}")
+            }
+        }
+        println()
+        println("Use `$programName <command> --help` for more information about a command.")
+    }
+
+    /**
+     * Print error message with optional coloring
+     */
+    private fun printError(message: String) {
+        println(colorize("Error: $message", Color.RED))
+    }
+
+    /**
+     * Print warning message with optional coloring
+     */
+    private fun printWarning(message: String) {
+        println(colorize("Warning: $message", Color.YELLOW))
+    }
+
+    /**
+     * Apply color to text if colors are enabled
+     */
+    private fun colorize(text: String, color: Color): String {
+        return if (config.colorsEnabled) {
+            "${color.code}$text${Color.RESET.code}"
+        } else {
+            text
+        }
+    }
+
+    /**
+     * ANSI color codes for terminal output
+     */
+    private enum class Color(val code: String) {
+        RESET("\u001B[0m"),
+        RED("\u001B[31m"),
+        GREEN("\u001B[32m"),
+        YELLOW("\u001B[33m"),
+        BOLD("\u001B[1m")
+    }
 }
 
+/**
+ * Custom exception for argument parsing errors
+ */
+class ArgumentParseException(message: String) : Exception(message)

src/main/kotlin/org/kargs/ParserConfig.kt

@@ -0,0 +1,17 @@
+package org.kargs
+
+/**
+ * Configuration class for customizing parser behavior
+ */
+data class ParserConfig(
+    val colorsEnabled: Boolean = true,
+    val strictMode: Boolean = false, // Whether to fail on unknown options
+    val helpOnEmpty: Boolean = true, // Show help when no args provided
+    val caseSensitive: Boolean = true,
+    val allowAbbreviations: Boolean = false, // Allow partial option matching
+    val programVersion: String? = null // Adds --version and -v flag if set
+) {
+    companion object {
+        val DEFAULT = ParserConfig()
+    }
+}

src/main/kotlin/org/kargs/Subcommand.kt

@@ -1,41 +1,110 @@
 package org.kargs
 
+
+/**
+ * Base class for defining subcommands with their options, flags, and arguments
+ *
+ * @param name The name for this subcommand
+ * @param description Help description for this subcommand
+ * @param aliases Alternative names for this subcommand
+ */
 abstract class Subcommand(
     val name: String,
     val description: String = "",
     val aliases: List<String> = emptyList()
 ) {
+    private val _options = mutableListOf<Option<*>>()
+    private val _flags = mutableListOf<Flag>()
+    private val _arguments = mutableListOf<Argument<*>>()
+
+    init {
+        require(name.isNotBlank()) { "Subcommand name cannot be blank" }
+    }
+
+    /**
+     * Register a property (option, flag, argument) with this subcommand
+     * Called automatically by property delagates
+     */
+    fun registerProperty(prop: KargsProperty<*>) {
+        when (prop) {
+            is Option<*> -> _options += prop
+            is Flag -> _flags += prop
+            is Argument<*> -> _arguments += prop
+        }
+    }
+
+    // Public read-only access to registered properties
+    val options: List<Option<*>> get() = _options
+    val flags: List<Flag> get() = _flags
+    val arguments: List<Argument<*>> get() = _arguments
+
+    /**
+     * Execute this subcommand - must be implemented by subclasses
+     */
     abstract fun execute()
 
-    open fun printHelp() {
-        println("Usage: $name [options] [arguments]")
-        if (description.isNotEmpty()) println(description)
-
-        val props = this::class.members.filterIsInstance<kotlin.reflect.KProperty<*>>()
-        val options = props.mapNotNull { it.getter.call(this) as? Option<*> }
-        val flags = props.mapNotNull { it.getter.call(this) as? Flag }
-        val arguments = props.mapNotNull { it.getter.call(this) as? Argument<*> }
+    /**
+     * Print help information for this subcommand
+     */
+    fun printHelp() {
+        println("Usage: $name [options]${if (arguments.isNotEmpty()) " ${arguments.joinToString(" ") { "<${it.name}>" }}" else ""}")
+        if (description.isNotEmpty()) {
+            println()
+            println(description)
+        }
 
         if (options.isNotEmpty()) {
-            println("\nOptions:")
-            options.forEach { o ->
-                println("  ${o.shortName?.let { "-$it, " } ?: ""}--${o.longName}\t${o.description}")
+            println()
+            println("Options:")
+            options.forEach { option ->
+                val shortName = option.shortName?.let { "-$it, " } ?: "    "
+                val required = if (option.required) " (required)" else ""
+                val defaultVal = option.getValueOrDefault()?.let { " [default: $it]" } ?: ""
+                println("  $shortName--${option.longName}")
+                option.description?.let { desc ->
+                    println("        $desc$required$defaultVal")
+                }
             }
         }
 
         if (flags.isNotEmpty()) {
-            println("\nFlags:")
-            flags.forEach { f ->
-                println("  ${f.shortName?.let { "-$it, " } ?: ""}--${f.longName}\t${f.description}")
+            println()
+            println("Flags:")
+            flags.forEach { flag ->
+                val shortName = flag.shortName?.let { "-$it, " } ?: "    "
+                println("  $shortName--${flag.longName}")
+                flag.description?.let { desc ->
+                    println("        $desc")
+                }
             }
         }
 
         if (arguments.isNotEmpty()) {
-            println("\nArguments:")
-            arguments.forEach { a ->
-                println("  ${a.name}\t${a.description}")
+            println()
+            println("Arguments:")
+            arguments.forEach { arg ->
+                val required = if (arg.required) " (required)" else " (optional)"
+                println("  ${arg.name}$required")
+                arg.description?.let { desc ->
+                    println("    $desc")
+                }
             }
         }
     }
-}
 
+    /**
+     * Validate all properties in this subcommand
+     * @return list of validation errors, empty if all valid
+     */
+    fun validate(): List<String> {
+        val errors = mutableListOf<String>()
+
+        (options + flags + arguments).forEach { prop -> 
+            prop.getValidationError()?.let { error -> 
+                errors.add(error)
+            }
+        }
+
+        return errors
+    }
+}

src/test/kotlin/org/kargs/tests/ArgTypeTest.kt

@@ -0,0 +1,107 @@
+package org.kargs.tests
+
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.ValueSource
+import org.kargs.ArgType
+import org.kargs.ArgumentParseException
+import kotlin.test.assertEquals
+
+class ArgTypeTest {
+    
+    @Test
+    fun `String type converts correctly`() {
+        val type = ArgType.String
+        assertEquals("hello", type.convert("hello"))
+        assertEquals("", type.convert(""))
+        assertEquals("123", type.convert("123"))
+    }
+    
+    @Test
+    fun `Int type converts valid integers`() {
+        val type = ArgType.Int
+        assertEquals(42, type.convert("42"))
+        assertEquals(-10, type.convert("-10"))
+        assertEquals(0, type.convert("0"))
+    }
+    
+    @Test
+    fun `Int type throws on invalid input`() {
+        val type = ArgType.Int
+        assertThrows<ArgumentParseException> { type.convert("not-a-number") }
+        assertThrows<ArgumentParseException> { type.convert("12.5") }
+        assertThrows<ArgumentParseException> { type.convert("") }
+    }
+    
+    @ParameterizedTest
+    @ValueSource(strings = ["true", "TRUE", "yes", "YES", "1", "on", "ON"])
+    fun `Boolean type converts true values`(input: String) {
+        val type = ArgType.Boolean
+        assertEquals(true, type.convert(input))
+    }
+    
+    @ParameterizedTest
+    @ValueSource(strings = ["false", "FALSE", "no", "NO", "0", "off", "OFF"])
+    fun `Boolean type converts false values`(input: String) {
+        val type = ArgType.Boolean
+        assertEquals(false, type.convert(input))
+    }
+    
+    @Test
+    fun `Boolean type throws on invalid input`() {
+        val type = ArgType.Boolean
+        assertThrows<ArgumentParseException> { type.convert("maybe") }
+        assertThrows<ArgumentParseException> { type.convert("2") }
+    }
+    
+    @Test
+    fun `Double type converts correctly`() {
+        val type = ArgType.Double
+        assertEquals(3.14, type.convert("3.14"))
+        assertEquals(-2.5, type.convert("-2.5"))
+        assertEquals(42.0, type.convert("42"))
+    }
+    
+    @Test
+    fun `Double type throws on invalid input`() {
+        val type = ArgType.Double
+        assertThrows<ArgumentParseException> { type.convert("not-a-number") }
+    }
+    
+    @Test
+    fun `IntRange validates bounds`() {
+        val type = ArgType.intRange(1, 10)
+        assertEquals(5, type.convert("5"))
+        assertEquals(1, type.convert("1"))
+        assertEquals(10, type.convert("10"))
+        
+        assertThrows<ArgumentParseException> { type.convert("0") }
+        assertThrows<ArgumentParseException> { type.convert("11") }
+        assertThrows<ArgumentParseException> { type.convert("-5") }
+    }
+    
+    @Test
+    fun `Choice validates options`() {
+        val type = ArgType.choice("red", "green", "blue")
+        assertEquals("red", type.convert("red"))
+        assertEquals("green", type.convert("green"))
+        assertEquals("blue", type.convert("blue"))
+        
+        assertThrows<ArgumentParseException> { type.convert("yellow") }
+        assertThrows<ArgumentParseException> { type.convert("RED") } // case sensitive
+    }
+    
+    @Test
+    fun `IntRange provides correct validation description`() {
+        val type = ArgType.intRange(5, 15)
+        assertEquals("integer between 5 and 15", type.getValidationDescription())
+    }
+    
+    @Test
+    fun `Choice provides correct validation description`() {
+        val type = ArgType.choice("apple", "banana", "cherry")
+        assertEquals("one of: apple, banana, cherry", type.getValidationDescription())
+    }
+}
+

src/test/kotlin/org/kargs/tests/ArgumentTest.kt

@@ -0,0 +1,78 @@
+package org.kargs.tests
+
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+import org.kargs.Argument
+import org.kargs.ArgType
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+import kotlin.test.assertFalse
+import kotlin.test.assertNull
+
+class ArgumentTest {
+    
+    @Test
+    fun `argument creation`() {
+        val arg = Argument(ArgType.String, "input", "Input file")
+        assertEquals("input", arg.name)
+        assertEquals("Input file", arg.description)
+        assertTrue(arg.required)
+    }
+    
+    @Test
+    fun `optional argument`() {
+        val arg = Argument(ArgType.String, "output", "Output file", required = false)
+        assertFalse(arg.required)
+        assertTrue(arg.isValid()) // optional and null is valid
+    }
+    
+    @Test
+    fun `argument parsing`() {
+        val arg = Argument(ArgType.Int, "count", "Item count")
+        assertNull(arg.value)
+        
+        arg.parseValue("42")
+        assertEquals(42, arg.value)
+    }
+    
+    @Test
+    fun `required argument validation`() {
+        val arg = Argument(ArgType.String, "required", "Required arg", required = true)
+        assertFalse(arg.isValid())
+        assertEquals("Argument 'required' is required", arg.getValidationError())
+        
+        arg.parseValue("value")
+        assertTrue(arg.isValid())
+        assertNull(arg.getValidationError())
+    }
+    
+    @Test
+    fun `argument throws on blank name`() {
+        assertThrows<IllegalArgumentException> {
+            Argument(ArgType.String, "", "Description")
+        }
+        
+        assertThrows<IllegalArgumentException> {
+            Argument(ArgType.String, "   ", "Description") // whitespace only
+        }
+    }
+    
+    @Test
+    fun `argument with choice type`() {
+        val arg = Argument(ArgType.choice("red", "green", "blue"), "color", "Color choice")
+        
+        arg.parseValue("red")
+        assertEquals("red", arg.value)
+        assertTrue(arg.isValid())
+    }
+    
+    @Test
+    fun `argument with range type`() {
+        val arg = Argument(ArgType.intRange(1, 100), "percentage", "Percentage value")
+        
+        arg.parseValue("50")
+        assertEquals(50, arg.value)
+        assertTrue(arg.isValid())
+    }
+}
+

src/test/kotlin/org/kargs/tests/FlagTest.kt

@@ -0,0 +1,103 @@
+package org.kargs.tests
+
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+import org.kargs.ArgumentParseException
+import org.kargs.Flag
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+import kotlin.test.assertFalse
+
+class FlagTest {
+    
+    @Test
+    fun `flag creation with default false`() {
+        val flag = Flag("verbose", "v", "Verbose output")
+        assertEquals("verbose", flag.longName)
+        assertEquals("v", flag.shortName)
+        assertEquals("Verbose output", flag.description)
+        assertEquals(false, flag.value)
+        assertFalse(flag.isSet())
+    }
+    
+    @Test
+    fun `flag creation with custom default`() {
+        val flag = Flag("enabled", defaultValue = true)
+        assertEquals(true, flag.value)
+        assertFalse(flag.isSet()) // not explicitly set, just default
+    }
+    
+    @Test
+    fun `setFlag updates value`() {
+        val flag = Flag("debug", "d")
+        assertEquals(false, flag.value)
+        
+        flag.setFlag()
+        assertEquals(true, flag.value)
+        assertTrue(flag.isSet())
+    }
+    
+    @Test
+    fun `parseValue handles boolean strings`() {
+        val flag = Flag("test")
+        
+        flag.parseValue("true")
+        assertEquals(true, flag.value)
+        
+        flag.parseValue("false")
+        assertEquals(false, flag.value)
+        
+        flag.parseValue("yes")
+        assertEquals(true, flag.value)
+        
+        flag.parseValue("no")
+        assertEquals(false, flag.value)
+        
+        flag.parseValue("1")
+        assertEquals(true, flag.value)
+        
+        flag.parseValue("0")
+        assertEquals(false, flag.value)
+    }
+    
+    @Test
+    fun `parseValue throws on invalid input`() {
+        val flag = Flag("test")
+        assertThrows<ArgumentParseException> {
+            flag.parseValue("maybe")
+        }
+        
+        assertThrows<ArgumentParseException> {
+            flag.parseValue("2")
+        }
+    }
+    
+    @Test
+    fun `flag throws on invalid names`() {
+        assertThrows<IllegalArgumentException> {
+            Flag("", "v") // blank long name
+        }
+        
+        assertThrows<IllegalArgumentException> {
+            Flag("--invalid") // long name with dashes
+        }
+        
+        assertThrows<IllegalArgumentException> {
+            Flag("valid", "ab") // short name too long
+        }
+        
+        assertThrows<IllegalArgumentException> {
+            Flag("valid", "-v") // short name with dash
+        }
+    }
+    
+    @Test
+    fun `flag isSet works correctly with defaults`() {
+        val flag = Flag("test", defaultValue = true)
+        assertFalse(flag.isSet()) // has default but not explicitly set
+        
+        flag.setFlag()
+        assertTrue(flag.isSet()) // now explicitly set
+    }
+}
+

src/test/kotlin/org/kargs/tests/IntegrationTest.kt

@@ -0,0 +1,128 @@
+package org.kargs.tests
+
+import org.junit.jupiter.api.Test
+import org.kargs.*
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+import kotlin.test.assertFalse
+
+class IntegrationTest {
+    
+    class ComplexCommand : Subcommand("complex", "Complex test command", listOf("c")) {
+        val input by Argument(ArgType.String, "input", "Input file")
+        val output by Argument(ArgType.String, "output", "Output file", required = false)
+        
+        val format by Option(ArgType.choice("json", "xml", "yaml"), "format", "f", "Output format", defaultValue = "json")
+        val threads by Option(ArgType.intRange(1, 32), "threads", "t", "Thread count", defaultValue = 4)
+        val timeout by Option(ArgType.Double, "timeout", description = "Timeout in seconds")
+        val config by Option(ArgType.String, "config", "c", "Config file", required = true)
+        
+        val verbose by Flag("verbose", "v", "Verbose output")
+        val dryRun by Flag("dry-run", "n", "Dry run mode")
+        val force by Flag("force", "f", "Force operation")
+        
+        var executed = false
+        
+        override fun execute() {
+            executed = true
+        }
+    }
+    
+    @Test
+    fun `complex command with all features`() {
+        val parser = Parser("myapp")
+        val cmd = ComplexCommand()
+        parser.subcommands(cmd)
+        
+        parser.parse(arrayOf(
+            "complex",
+            "--config", "/path/to/config.yml",
+            "--format", "xml",
+            "--threads", "8",
+            "--timeout", "30.5",
+            "--verbose",
+            "--dry-run",
+            "input.txt",
+            "output.xml"
+        ))
+        
+        assertTrue(cmd.executed)
+        assertEquals("input.txt", cmd.input)
+        assertEquals("output.xml", cmd.output)
+        assertEquals("/path/to/config.yml", cmd.config)
+        assertEquals("xml", cmd.format)
+        assertEquals(8, cmd.threads)
+        assertEquals(30.5, cmd.timeout)
+        assertEquals(true, cmd.verbose)
+        assertEquals(true, cmd.dryRun)
+        assertEquals(false, cmd.force)
+    }
+    
+    @Test
+    fun `complex command with short options and combined flags`() {
+        val parser = Parser("myapp")
+        val cmd = ComplexCommand()
+        parser.subcommands(cmd)
+        
+        parser.parse(arrayOf(
+            "c", // using alias
+            "-c", "/config.yml",
+            "-f", "yaml",
+            "-t", "16",
+            "-vnf", // combined flags: verbose, dry-run (n), force
+            "input.txt"
+        ))
+        
+        assertTrue(cmd.executed)
+        assertEquals("input.txt", cmd.input)
+        assertEquals("/config.yml", cmd.config)
+        assertEquals("yaml", cmd.format)
+        assertEquals(16, cmd.threads)
+        assertEquals(true, cmd.verbose)
+        assertEquals(true, cmd.dryRun)
+        assertEquals(true, cmd.force)
+    }
+    
+    @Test
+    fun `multiple commands in same parser`() {
+        val parser = Parser("tool")
+        val buildCmd = TestUtils.TestSubcommand("build", "Build project")
+        val testCmd = TestUtils.TestSubcommand("test", "Run tests")
+        val deployCmd = TestUtils.TestSubcommand("deploy", "Deploy project")
+        
+        parser.subcommands(buildCmd, testCmd, deployCmd)
+        
+        // Test build command
+        parser.parse(arrayOf("build", "--required", "value", "src/"))
+        assertTrue(buildCmd.executed)
+        
+        // Reset and test different command
+        buildCmd.executed = false
+        parser.parse(arrayOf("test", "--required", "value", "tests/"))
+        assertTrue(testCmd.executed)
+        assertFalse(buildCmd.executed) // should not be executed again
+    }
+    
+    @Test
+    fun `validation works end-to-end`() {
+        val parser = Parser("app")
+        val cmd = ComplexCommand()
+        parser.subcommands(cmd)
+        
+        // Should validate all constraints
+        parser.parse(arrayOf(
+            "complex",
+            "--config", "config.yml",
+            "--format", "json", // valid choice
+            "--threads", "8",   // valid range
+            "--timeout", "15.5", // valid double
+            "input.txt"
+        ))
+        
+        assertTrue(cmd.executed)
+        assertEquals("json", cmd.format)
+        assertEquals(8, cmd.threads)
+        assertEquals(15.5, cmd.timeout)
+    }
+}
+

src/test/kotlin/org/kargs/tests/OptionTest.kt

@@ -0,0 +1,95 @@
+package org.kargs.tests
+
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+import org.kargs.ArgType
+import org.kargs.Option
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+import kotlin.test.assertFalse
+import kotlin.test.assertNull
+
+class OptionTest {
+    
+    @Test
+    fun `option creation with valid parameters`() {
+        val option = Option(ArgType.String, "output", "o", "Output file", required = true)
+        assertEquals("output", option.longName)
+        assertEquals("o", option.shortName)
+        assertEquals("Output file", option.description)
+        assertTrue(option.required)
+    }
+    
+    @Test
+    fun `option with default value`() {
+        val option = Option(ArgType.Int, "threads", "t", "Thread count", defaultValue = 4)
+        assertEquals(4, option.value)
+        assertEquals(4, option.getValueOrDefault())
+        assertFalse(option.isSet())
+    }
+    
+    @Test
+    fun `option parsing updates value`() {
+        val option = Option(ArgType.String, "name", "n")
+        assertNull(option.value)
+        
+        option.parseValue("test")
+        assertEquals("test", option.value)
+        assertTrue(option.isSet())
+    }
+    
+    @Test
+    fun `option validation for required field`() {
+        val option = Option(ArgType.String, "required", required = true)
+        assertFalse(option.isValid())
+        assertEquals("Option --required is required", option.getValidationError())
+        
+        option.parseValue("value")
+        assertTrue(option.isValid())
+        assertNull(option.getValidationError())
+    }
+    
+    @Test
+    fun `option throws on invalid names`() {
+        assertThrows<IllegalArgumentException> {
+            Option(ArgType.String, "", "o") // blank long name
+        }
+        
+        assertThrows<IllegalArgumentException> {
+            Option(ArgType.String, "--invalid", "o") // long name with dashes
+        }
+        
+        assertThrows<IllegalArgumentException> {
+            Option(ArgType.String, "valid", "ab") // short name too long
+        }
+        
+        assertThrows<IllegalArgumentException> {
+            Option(ArgType.String, "valid", "-o") // short name with dash
+        }
+    }
+    
+    @Test
+    fun `option with range type validation`() {
+        val option = Option(ArgType.intRange(1, 10), "count", "c", "Item count")
+        
+        option.parseValue("5")
+        assertEquals(5, option.value)
+        assertTrue(option.isValid())
+        
+        // Test that the option itself doesn't validate the range (ArgType does)
+        // The validation happens during parsing
+    }
+    
+    @Test
+    fun `option isSet works correctly with defaults`() {
+        val option = Option(ArgType.String, "mode", defaultValue = "default")
+        assertFalse(option.isSet()) // has default but not explicitly set
+        
+        option.parseValue("custom")
+        assertTrue(option.isSet()) // now explicitly set
+        
+        option.parseValue("default") // set to same as default
+        assertTrue(option.isSet()) // still considered "set"
+    }
+}
+

src/test/kotlin/org/kargs/tests/ParserConfigTest.kt

@@ -0,0 +1,107 @@
+package org.kargs.tests
+
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+import org.kargs.ArgumentParseException
+import org.kargs.Parser
+import org.kargs.ParserConfig
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+import kotlin.test.assertFalse
+
+class ParserConfigTest {
+    
+    @Test
+    fun `default config values`() {
+        val config = ParserConfig.DEFAULT
+        assertTrue(config.colorsEnabled)
+        assertFalse(config.strictMode)
+        assertTrue(config.helpOnEmpty)
+        assertTrue(config.caseSensitive)
+        assertFalse(config.allowAbbreviations)
+    }
+    
+    @Test
+    fun `custom config values`() {
+        val config = ParserConfig(
+            colorsEnabled = false,
+            strictMode = true,
+            helpOnEmpty = false,
+            caseSensitive = false,
+            allowAbbreviations = true
+        )
+        
+        assertFalse(config.colorsEnabled)
+        assertTrue(config.strictMode)
+        assertFalse(config.helpOnEmpty)
+        assertFalse(config.caseSensitive)
+        assertTrue(config.allowAbbreviations)
+    }
+    
+    @Test
+    fun `strict mode affects unknown options`() {
+        val strictParser = Parser("test", ParserConfig(strictMode = true))
+        val lenientParser = Parser("test", ParserConfig(strictMode = false))
+        
+        val testCmd = TestUtils.TestSubcommand()
+        strictParser.subcommands(testCmd)
+        lenientParser.subcommands(testCmd)
+        
+        // Strict mode should throw
+        assertThrows<ArgumentParseException> {
+            strictParser.parse(arrayOf("test", "--unknown", "value", "--required", "req", "input.txt"))
+        }
+        
+        // Lenient mode should warn but continue
+        val output = TestUtils.captureOutput {
+            lenientParser.parse(arrayOf("test", "--unknown", "value", "--required", "req", "input.txt"))
+        }
+        assertTrue(output.contains("Warning"))
+        assertTrue(testCmd.executed)
+    }
+    
+    @Test
+    fun `helpOnEmpty config affects empty args behavior`() {
+        val helpParser = Parser("test", ParserConfig(helpOnEmpty = true))
+        val noHelpParser = Parser("test", ParserConfig(helpOnEmpty = false))
+        
+        val testCmd = TestUtils.TestSubcommand()
+        helpParser.subcommands(testCmd)
+        noHelpParser.subcommands(testCmd)
+        
+        // With helpOnEmpty = true, should show help
+        val helpOutput = TestUtils.captureOutput {
+            helpParser.parse(arrayOf())
+        }
+        assertTrue(helpOutput.contains("Usage:"))
+        
+        // With helpOnEmpty = false, should do nothing
+        val noHelpOutput = TestUtils.captureOutput {
+            noHelpParser.parse(arrayOf())
+        }
+        assertEquals("", noHelpOutput)
+    }
+    
+    @Test
+    fun `case sensitivity affects command matching`() {
+        val caseSensitiveParser = Parser("test", ParserConfig(caseSensitive = true))
+        val caseInsensitiveParser = Parser("test", ParserConfig(caseSensitive = false))
+        
+        val testCmd = TestUtils.TestSubcommand("Test") // capital T
+        caseSensitiveParser.subcommands(testCmd)
+        caseInsensitiveParser.subcommands(testCmd)
+        
+        // Case sensitive should not match "test" to "Test"
+        val sensitiveOutput = TestUtils.captureOutput {
+            caseSensitiveParser.parse(arrayOf("test", "--required", "value", "input.txt"))
+        }
+        assertTrue(sensitiveOutput.contains("Unknown command"))
+        assertFalse(testCmd.executed)
+        
+        // Case insensitive should match
+        testCmd.executed = false // reset
+        caseInsensitiveParser.parse(arrayOf("test", "--required", "value", "input.txt"))
+        assertTrue(testCmd.executed)
+    }
+}
+

src/test/kotlin/org/kargs/tests/ParserTest.kt

@@ -0,0 +1,175 @@
+package org.kargs.tests
+
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.assertThrows
+import org.kargs.ArgumentParseException
+import org.kargs.Parser
+import org.kargs.ParserConfig
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+import kotlin.test.assertFalse
+
+class ParserTest {
+    
+    private lateinit var parser: Parser
+    private lateinit var testCmd: TestUtils.TestSubcommand
+    
+    @BeforeEach
+    fun setup() {
+        parser = Parser("testapp")
+        testCmd = TestUtils.TestSubcommand()
+        parser.subcommands(testCmd)
+    }
+    
+    @Test
+    fun `parse basic command with required option`() {
+        parser.parse(arrayOf("test", "--required", "value", "input.txt"))
+        
+        assertTrue(testCmd.executed)
+        assertEquals("value", testCmd.requiredOpt)
+        assertEquals("input.txt", testCmd.inputArg)
+    }
+    
+    @Test
+    fun `parse command with short options`() {
+        parser.parse(arrayOf("test", "-r", "required", "-s", "string", "-n", "42", "input.txt"))
+        
+        assertTrue(testCmd.executed)
+        assertEquals("required", testCmd.requiredOpt)
+        assertEquals("string", testCmd.stringOpt)
+        assertEquals(42, testCmd.intOpt)
+        assertEquals("input.txt", testCmd.inputArg)
+    }
+    
+    @Test
+    fun `parse command with flags`() {
+        parser.parse(arrayOf("test", "--required", "value", "--verbose", "--debug", "input.txt"))
+        
+        assertTrue(testCmd.executed)
+        assertEquals(true, testCmd.verboseFlag)
+        assertEquals(true, testCmd.debugFlag)
+        assertEquals(false, testCmd.forceFlag) // not set, should be default
+    }
+    
+    @Test
+    fun `parse command with combined short flags`() {
+        parser.parse(arrayOf("test", "-r", "value", "-vf", "input.txt"))
+        
+        assertTrue(testCmd.executed)
+        assertEquals("value", testCmd.requiredOpt)
+        assertEquals(true, testCmd.verboseFlag)
+        assertEquals(true, testCmd.forceFlag)
+    }
+    
+    @Test
+    fun `parse command with all argument types`() {
+        parser.parse(arrayOf(
+            "test", 
+            "--required", "req",
+            "--string", "hello",
+            "--number", "123",
+            "--range", "5",
+            "--choice", "b",
+            "--double", "3.14",
+            "--verbose",
+            "input.txt",
+            "output.txt"
+        ))
+        
+        assertTrue(testCmd.executed)
+        assertEquals("req", testCmd.requiredOpt)
+        assertEquals("hello", testCmd.stringOpt)
+        assertEquals(123, testCmd.intOpt)
+        assertEquals(5, testCmd.rangeOpt)
+        assertEquals("b", testCmd.choiceOpt)
+        assertEquals(3.14, testCmd.doubleOpt)
+        assertEquals(true, testCmd.verboseFlag)
+        assertEquals("input.txt", testCmd.inputArg)
+        assertEquals("output.txt", testCmd.outputArg)
+    }
+    
+    @Test
+    fun `throws exception when required option missing`() {
+        assertThrows<ArgumentParseException> {
+            parser.parse(arrayOf("test", "input.txt"))
+        }
+        assertFalse(testCmd.executed)
+    }
+    
+    @Test
+    fun `throws exception on invalid integer`() {
+        assertThrows<ArgumentParseException> {
+            parser.parse(arrayOf("test", "--required", "value", "--number", "not-a-number", "input.txt"))
+        }
+    }
+    
+    @Test
+    fun `throws exception on out of range value`() {
+        assertThrows<ArgumentParseException> {
+            parser.parse(arrayOf("test", "--required", "value", "--range", "15", "input.txt"))
+        }
+    }
+    
+    @Test
+    fun `throws exception on invalid choice`() {
+        assertThrows<ArgumentParseException> {
+            parser.parse(arrayOf("test", "--required", "value", "--choice", "invalid", "input.txt"))
+        }
+    }
+    
+    @Test
+    fun `handles unknown command`() {
+        val output = TestUtils.captureOutput {
+            parser.parse(arrayOf("unknown", "arg"))
+        }
+        assertTrue(output.contains("Unknown command: unknown"))
+    }
+    
+    @Test
+    fun `shows global help on empty args`() {
+        val output = TestUtils.captureOutput {
+            parser.parse(arrayOf())
+        }
+        assertTrue(output.contains("Usage: testapp <command>"))
+        assertTrue(output.contains("test"))
+    }
+    
+    @Test
+    fun `shows global help on --help`() {
+        val output = TestUtils.captureOutput {
+            parser.parse(arrayOf("--help"))
+        }
+        assertTrue(output.contains("Usage: testapp <command>"))
+    }
+    
+    @Test
+    fun `handles command aliases`() {
+        val aliasCmd = TestUtils.TestSubcommand("build", "Build command", listOf("b", "compile"))
+        parser.subcommands(aliasCmd)
+        
+        // Test main name
+        parser.parse(arrayOf("build", "--required", "value", "input.txt"))
+        assertTrue(aliasCmd.executed)
+        
+        // Reset and test alias
+        aliasCmd.executed = false
+        parser.parse(arrayOf("b", "--required", "value", "input.txt"))
+        assertTrue(aliasCmd.executed)
+    }
+    
+    @Test
+    fun `handles missing option value`() {
+        assertThrows<ArgumentParseException> {
+            parser.parse(arrayOf("test", "--required"))
+        }
+    }
+    
+    @Test
+    fun `handles missing short option value`() {
+        assertThrows<ArgumentParseException> {
+            parser.parse(arrayOf("test", "-r"))
+        }
+    }
+}
+

src/test/kotlin/org/kargs/tests/SubcommandTest.kt

@@ -0,0 +1,159 @@
+package org.kargs.tests
+
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+import org.kargs.*
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+import kotlin.test.assertFalse
+import kotlin.test.assertNull
+
+class SubcommandTest {
+    
+    @Test
+    fun `subcommand creation with valid parameters`() {
+        val cmd = TestUtils.TestSubcommand("build", "Build the project", listOf("b", "compile"))
+        assertEquals("build", cmd.name)
+        assertEquals("Build the project", cmd.description)
+        assertEquals(listOf("b", "compile"), cmd.aliases)
+    }
+    
+    @Test
+    fun `subcommand throws on blank name`() {
+        assertThrows<IllegalArgumentException> {
+            TestUtils.TestSubcommand("", "Description")
+        }
+        
+        assertThrows<IllegalArgumentException> {
+            TestUtils.TestSubcommand("   ", "Description") // whitespace only
+        }
+    }
+    
+    @Test
+    fun `subcommand registers properties correctly`() {
+        val cmd = TestUtils.TestSubcommand()
+        
+        // Properties should be registered automatically via delegates
+        assertTrue(cmd.options.isNotEmpty())
+        assertTrue(cmd.flags.isNotEmpty())
+        assertTrue(cmd.arguments.isNotEmpty())
+        
+        // Check specific properties are registered
+        assertTrue(cmd.options.any { it.longName == "required" })
+        assertTrue(cmd.flags.any { it.longName == "verbose" })
+        assertTrue(cmd.arguments.any { it.name == "input" })
+    }
+    
+    @Test
+    fun `subcommand validation works`() {
+        val cmd = TestUtils.TestSubcommand()
+        
+        // Should have validation errors for required fields
+        val errors = cmd.validate()
+        assertTrue(errors.isNotEmpty())
+        assertTrue(errors.any { it.contains("required") })
+        
+        // Set required values through parsing (the proper way)
+        val requiredOption = cmd.options.find { it.longName == "required" }
+        val inputArgument = cmd.arguments.find { it.name == "input" }
+        
+        requiredOption?.parseValue("value")
+        inputArgument?.parseValue("input.txt")
+        
+        // Should now be valid
+        val errorsAfter = cmd.validate()
+        assertTrue(errorsAfter.isEmpty())
+    }
+    
+    @Test
+    fun `subcommand help generation`() {
+        val cmd = TestUtils.TestSubcommand("test", "Test command for validation")
+        
+        val helpOutput = TestUtils.captureOutput {
+            cmd.printHelp()
+        }
+        
+        assertTrue(helpOutput.contains("Usage: test [options]"))
+        assertTrue(helpOutput.contains("Test command for validation"))
+        assertTrue(helpOutput.contains("Options:"))
+        assertTrue(helpOutput.contains("--required"))
+        assertTrue(helpOutput.contains("Flags:"))
+        assertTrue(helpOutput.contains("--verbose"))
+        assertTrue(helpOutput.contains("Arguments:"))
+        assertTrue(helpOutput.contains("input"))
+    }
+    
+    @Test
+    fun `subcommand property access works`() {
+        val cmd = TestUtils.TestSubcommand()
+        
+        // Initially null/default values
+        assertNull(cmd.requiredOpt)
+        assertEquals(false, cmd.verboseFlag)
+        assertNull(cmd.inputArg)
+        
+        // Set values through parsing (simulating real usage)
+        val requiredOption = cmd.options.find { it.longName == "required" }
+        val verboseFlag = cmd.flags.find { it.longName == "verbose" }
+        val inputArgument = cmd.arguments.find { it.name == "input" }
+        
+        requiredOption?.parseValue("test")
+        verboseFlag?.setFlag()
+        inputArgument?.parseValue("file.txt")
+        
+        // Values should be accessible
+        assertEquals("test", cmd.requiredOpt)
+        assertEquals(true, cmd.verboseFlag)
+        assertEquals("file.txt", cmd.inputArg)
+    }
+    
+    @Test
+    fun `subcommand property types are correct`() {
+        val cmd = TestUtils.TestSubcommand()
+        
+        // Check that we can find properties by their characteristics
+        val stringOption = cmd.options.find { it.longName == "string" }
+        val intOption = cmd.options.find { it.longName == "number" }
+        val rangeOption = cmd.options.find { it.longName == "range" }
+        val choiceOption = cmd.options.find { it.longName == "choice" }
+        
+        assertTrue(stringOption != null)
+        assertTrue(intOption != null)
+        assertTrue(rangeOption != null)
+        assertTrue(choiceOption != null)
+        
+        // Test parsing different types
+        stringOption?.parseValue("hello")
+        intOption?.parseValue("42")
+        rangeOption?.parseValue("5")
+        choiceOption?.parseValue("b")
+        
+        assertEquals("hello", cmd.stringOpt)
+        assertEquals(42, cmd.intOpt)
+        assertEquals(5, cmd.rangeOpt)
+        assertEquals("b", cmd.choiceOpt)
+    }
+    
+    @Test
+    fun `subcommand execution tracking works`() {
+        val cmd = TestUtils.TestSubcommand()
+        
+        assertFalse(cmd.executed)
+        assertTrue(cmd.executionData.isEmpty())
+        
+        // Set some values and execute
+        val requiredOption = cmd.options.find { it.longName == "required" }
+        val inputArgument = cmd.arguments.find { it.name == "input" }
+        
+        requiredOption?.parseValue("test")
+        inputArgument?.parseValue("input.txt")
+        
+        cmd.execute()
+        
+        assertTrue(cmd.executed)
+        assertTrue(cmd.executionData.isNotEmpty())
+        assertEquals("test", cmd.executionData["requiredOpt"])
+        assertEquals("input.txt", cmd.executionData["inputArg"])
+    }
+}
+

src/test/kotlin/org/kargs/tests/TestUtils.kt

@@ -0,0 +1,73 @@
+package org.kargs.tests
+
+import org.kargs.*
+import java.io.ByteArrayOutputStream
+import java.io.PrintStream
+
+/**
+ * Utility functions for testing
+ */
+object TestUtils {
+    
+    /**
+     * Capture console output during execution
+     */
+    fun captureOutput(block: () -> Unit): String {
+        val originalOut = System.out
+        val outputStream = ByteArrayOutputStream()
+        System.setOut(PrintStream(outputStream))
+        
+        try {
+            block()
+            return outputStream.toString().trim()
+        } finally {
+            System.setOut(originalOut)
+        }
+    }
+    
+    /**
+     * Create a test subcommand for testing purposes
+     */
+    class TestSubcommand(
+        name: String = "test",
+        description: String = "Test command",
+        aliases: List<String> = emptyList()
+    ) : Subcommand(name, description, aliases) {
+        
+        var executed = false
+        var executionData: Map<String, Any?> = emptyMap()
+        
+        // Test properties
+        val stringOpt by Option(ArgType.String, "string", "s", "String option")
+        val requiredOpt by Option(ArgType.String, "required", "r", "Required option", required = true)
+        val intOpt by Option(ArgType.Int, "number", "n", "Integer option")
+        val rangeOpt by Option(ArgType.intRange(1, 10), "range", description = "Range option")
+        val choiceOpt by Option(ArgType.choice("a", "b", "c"), "choice", "c", "Choice option")
+        val doubleOpt by Option(ArgType.Double, "double", "d", "Double option")
+        
+        val verboseFlag by Flag("verbose", "v", "Verbose flag")
+        val debugFlag by Flag("debug", description = "Debug flag")
+        val forceFlag by Flag("force", "f", "Force flag", defaultValue = false)
+        
+        val inputArg by Argument(ArgType.String, "input", "Input argument")
+        val outputArg by Argument(ArgType.String, "output", "Output argument", required = false)
+        
+        override fun execute() {
+            executed = true
+            executionData = mapOf(
+                "stringOpt" to stringOpt,
+                "requiredOpt" to requiredOpt,
+                "intOpt" to intOpt,
+                "rangeOpt" to rangeOpt,
+                "choiceOpt" to choiceOpt,
+                "doubleOpt" to doubleOpt,
+                "verboseFlag" to verboseFlag,
+                "debugFlag" to debugFlag,
+                "forceFlag" to forceFlag,
+                "inputArg" to inputArg,
+                "outputArg" to outputArg
+            )
+        }
+    }
+}
+