feat: updated bool parsing and added tests

tests/test_main.rs

@@ -0,0 +1,43 @@
+#[cfg(test)]
+mod test_main {
+    use envkit::*;
+
+    #[test]
+    /// Tests that `get` successfully retrieves an existing environment variable.
+    fn test_get() {
+        let env = EnvLoader;
+        
+        unsafe {
+            std::env::set_var("TEST_VAR", "test_value");
+        }
+        
+        assert_eq!(env.get::<String>("TEST_VAR"), Ok("test_value".to_string()));
+    }
+
+    #[test]
+    /// Tests that `get_or` returns the default value when the environment variable is missing.
+    fn test_get_or() {
+        let env = EnvLoader;
+        
+        unsafe {
+            std::env::remove_var("MISSING_VAR");
+            std::env::set_var("TEST_VAR", "test_value");
+        }
+        
+        assert_eq!(env.get_or::<String>("MISSING_VAR", "default".to_string()), "default".to_string());
+        assert_eq!(env.get_or::<String>("TEST_VAR", "default".to_string()), "test_value".to_string());
+    }
+
+    #[test]
+    /// Tests that `get_opt` returns `Some` when the environment variable exists.
+    fn test_get_opt() {
+        let env = EnvLoader;
+       
+        unsafe {
+            std::env::set_var("OPTIONAL_VAR", "optional_value");
+        } 
+
+        assert_eq!(env.get_opt::<String>("OPTIONAL_VAR"), Some("optional_value".to_string()));
+        assert_eq!(env.get_opt::<bool>("DEV"), None);
+    }
+}