diff --git a/phpunit/src/ArgInfoTest.php b/phpunit/src/ArgInfoTest.php
new file mode 100644
index 00000000..0eed83d0
--- /dev/null
+++ b/phpunit/src/ArgInfoTest.php
@@ -0,0 +1,114 @@
+<?php
+
+namespace PhpAot\Tests;
+
+use PHPUnit\Framework\TestCase;
+use PhpAot\Php\ArgInfo;
+
+class ArgInfoTest extends TestCase
+{
+    public function testDefaultBooleanProperties(): void
+    {
+        $arg = new ArgInfo();
+        // Set required string properties first (they have no defaults)
+        $arg->name = '';
+        $arg->type = '';
+
+        // default values for implicitly-initialized fields
+        $this->assertEquals('', $arg->default);
+        $this->assertNull($arg->defaultValue);
+        $this->assertEquals('', $arg->class);
+        $this->assertFalse($arg->byRef);
+        $this->assertFalse($arg->variadic);
+        $this->assertFalse($arg->nullable);
+        $this->assertFalse($arg->property);
+        $this->assertFalse($arg->unsafePtr);
+    }
+
+    public function testNameAndType(): void
+    {
+        $arg = new ArgInfo();
+        $arg->name = 'value';
+        $arg->type = 'php::Int';
+
+        $this->assertEquals('value', $arg->name);
+        $this->assertEquals('php::Int', $arg->type);
+    }
+
+    public function testDefaultValues(): void
+    {
+        $arg = new ArgInfo();
+        $arg->default = '0';
+
+        $this->assertEquals('0', $arg->default);
+    }
+
+    public function testClass(): void
+    {
+        $arg = new ArgInfo();
+        $arg->class = 'DateTime';
+
+        $this->assertEquals('DateTime', $arg->class);
+    }
+
+    public function testByRef(): void
+    {
+        $arg = new ArgInfo();
+        $this->assertFalse($arg->byRef);
+
+        $arg->byRef = true;
+        $this->assertTrue($arg->byRef);
+    }
+
+    public function testVariadic(): void
+    {
+        $arg = new ArgInfo();
+        $this->assertFalse($arg->variadic);
+
+        $arg->variadic = true;
+        $this->assertTrue($arg->variadic);
+    }
+
+    public function testNullable(): void
+    {
+        $arg = new ArgInfo();
+        $this->assertFalse($arg->nullable);
+
+        $arg->nullable = true;
+        $this->assertTrue($arg->nullable);
+    }
+
+    public function testProperty(): void
+    {
+        $arg = new ArgInfo();
+        $this->assertFalse($arg->property);
+
+        $arg->property = true;
+        $this->assertTrue($arg->property);
+    }
+
+    public function testUnsafePtr(): void
+    {
+        $arg = new ArgInfo();
+        $this->assertFalse($arg->unsafePtr);
+
+        $arg->unsafePtr = true;
+        $this->assertTrue($arg->unsafePtr);
+    }
+
+    public function testAllFlagsCombined(): void
+    {
+        $arg = new ArgInfo();
+        $arg->name = 'args';
+        $arg->type = 'php::Var';
+        $arg->variadic = true;
+        $arg->byRef = true;
+        $arg->nullable = true;
+
+        $this->assertEquals('args', $arg->name);
+        $this->assertEquals('php::Var', $arg->type);
+        $this->assertTrue($arg->variadic);
+        $this->assertTrue($arg->byRef);
+        $this->assertTrue($arg->nullable);
+    }
+}
diff --git a/phpunit/src/Context/FunctionContextTest.php b/phpunit/src/Context/FunctionContextTest.php
new file mode 100644
index 00000000..420cd85c
--- /dev/null
+++ b/phpunit/src/Context/FunctionContextTest.php
@@ -0,0 +1,113 @@
+<?php
+
+namespace PhpAot\Tests\Context;
+
+use PHPUnit\Framework\TestCase;
+use PhpAot\Php\Context\FunctionContext;
+use PhpAot\Php\Context\ScopeContext;
+
+class FunctionContextTest extends TestCase
+{
+    public function testConstructInitializesAllProperties(): void
+    {
+        $ctx = new FunctionContext();
+
+        $this->assertEmpty($ctx->objects);
+        $this->assertEmpty($ctx->stdArrays);
+        $this->assertEmpty($ctx->stdContainers);
+        $this->assertEmpty($ctx->localVars);
+        $this->assertEmpty($ctx->staticVars);
+        $this->assertEmpty($ctx->globalVars);
+        $this->assertEmpty($ctx->ceWrappers);
+        $this->assertEmpty($ctx->arguments);
+        $this->assertEmpty($ctx->beforeStmtLines);
+        $this->assertEmpty($ctx->afterStmtLines);
+        $this->assertEmpty($ctx->objectProps);
+        $this->assertEmpty($ctx->scopeLayouts);
+
+        $this->assertSame(0, $ctx->tmpVarIndex);
+        $this->assertSame(0, $ctx->scopeLevel);
+        $this->assertFalse($ctx->inLoop);
+        $this->assertFalse($ctx->inClosure);
+        $this->assertFalse($ctx->inAssignExpr);
+    }
+
+    public function testEnterScopeIncrementsLevel(): void
+    {
+        $ctx = new FunctionContext();
+        $this->assertSame(0, $ctx->scopeLevel);
+
+        $ctx->enterScope();
+        $this->assertSame(1, $ctx->scopeLevel);
+        $this->assertArrayHasKey(0, $ctx->scopeLayouts);
+        $this->assertInstanceOf(ScopeContext::class, $ctx->scopeLayouts[0]);
+
+        $ctx->enterScope();
+        $this->assertSame(2, $ctx->scopeLevel);
+        $this->assertArrayHasKey(0, $ctx->scopeLayouts);
+        $this->assertArrayHasKey(1, $ctx->scopeLayouts);
+    }
+
+    public function testLeaveScopeDecrementsLevel(): void
+    {
+        $ctx = new FunctionContext();
+        $ctx->enterScope();
+        $ctx->enterScope();
+        $this->assertSame(2, $ctx->scopeLevel);
+
+        $ctx->leaveScope();
+        $this->assertSame(1, $ctx->scopeLevel);
+
+        $ctx->leaveScope();
+        $this->assertSame(0, $ctx->scopeLevel);
+    }
+
+    public function testMutableProperties(): void
+    {
+        $ctx = new FunctionContext();
+
+        $ctx->inLoop = true;
+        $this->assertTrue($ctx->inLoop);
+
+        $ctx->inClosure = true;
+        $this->assertTrue($ctx->inClosure);
+
+        $ctx->inAssignExpr = true;
+        $this->assertTrue($ctx->inAssignExpr);
+
+        $ctx->tmpVarIndex = 5;
+        $this->assertSame(5, $ctx->tmpVarIndex);
+    }
+
+    public function testLocalVarsManipulation(): void
+    {
+        $ctx = new FunctionContext();
+        $ctx->localVars['x'] = 'php::Int';
+        $ctx->localVars['name'] = 'php::Str';
+
+        $this->assertArrayHasKey('x', $ctx->localVars);
+        $this->assertArrayHasKey('name', $ctx->localVars);
+        $this->assertEquals('php::Int', $ctx->localVars['x']);
+        $this->assertEquals('php::Str', $ctx->localVars['name']);
+    }
+
+    public function testObjectsMap(): void
+    {
+        $ctx = new FunctionContext();
+        $ctx->objects['obj1'] = 'stdClass';
+        $ctx->objects['obj2'] = 'DateTime';
+
+        $this->assertCount(2, $ctx->objects);
+        $this->assertEquals('stdClass', $ctx->objects['obj1']);
+    }
+
+    public function testBeforeAfterStmtLines(): void
+    {
+        $ctx = new FunctionContext();
+        $ctx->beforeStmtLines[] = 'int x = 1;';
+        $ctx->afterStmtLines[] = 'x = 0;';
+
+        $this->assertCount(1, $ctx->beforeStmtLines);
+        $this->assertCount(1, $ctx->afterStmtLines);
+    }
+}
diff --git a/phpunit/src/Context/ScopeContextTest.php b/phpunit/src/Context/ScopeContextTest.php
new file mode 100644
index 00000000..24356f0e
--- /dev/null
+++ b/phpunit/src/Context/ScopeContextTest.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace PhpAot\Tests\Context;
+
+use PHPUnit\Framework\TestCase;
+use PhpAot\Php\Context\ScopeContext;
+
+class ScopeContextTest extends TestCase
+{
+    public function testCanInstantiate(): void
+    {
+        $scope = new ScopeContext();
+        $this->assertInstanceOf(ScopeContext::class, $scope);
+    }
+}
diff --git a/phpunit/src/Entity/ClassDefTest.php b/phpunit/src/Entity/ClassDefTest.php
new file mode 100644
index 00000000..18edb767
--- /dev/null
+++ b/phpunit/src/Entity/ClassDefTest.php
@@ -0,0 +1,133 @@
+<?php
+
+namespace PhpAot\Tests\Entity;
+
+use PHPUnit\Framework\TestCase;
+use PhpAot\Php\Entity\ClassDef;
+use PhpAot\Php\Entity\MethodDef;
+use PhpAot\Php\Entity\PropertyDef;
+use PhpAot\Php\Entity\ConstantDef;
+use PhpAot\Php\Entity\FunctionDef;
+use PhpParser\Modifiers;
+
+class ClassDefTest extends TestCase
+{
+    public function testConstructDefaults(): void
+    {
+        $class = new ClassDef('Foo', Modifiers::PUBLIC);
+        $this->assertEquals('Foo', $class->name);
+        $this->assertEquals('', $class->namespace);
+        $this->assertSame(Modifiers::PUBLIC, $class->flags);
+        $this->assertEquals('', $class->extends);
+        $this->assertEmpty($class->implements);
+        $this->assertEmpty($class->methods);
+        $this->assertEmpty($class->properties);
+        $this->assertEmpty($class->constants);
+        $this->assertFalse($class->enum);
+        $this->assertFalse($class->requireCtor);
+        $this->assertFalse($class->inheritedFromInternalClass);
+        $this->assertNull($class->trait);
+    }
+
+    public function testConstructWithNamespace(): void
+    {
+        $class = new ClassDef('Bar', Modifiers::PUBLIC, 'App\\Lib');
+        $this->assertEquals('Bar', $class->name);
+        $this->assertEquals('App\\Lib', $class->namespace);
+    }
+
+    public function testPropertyContextIsInitialized(): void
+    {
+        $class = new ClassDef('Foo', Modifiers::PUBLIC);
+        $this->assertNotNull($class->propertyContext);
+        $this->assertInstanceOf(\PhpAot\Php\Context\FunctionContext::class, $class->propertyContext);
+    }
+
+    public function testGetNamespacedNameInheritedFromClassLikeDef(): void
+    {
+        $class = new ClassDef('Foo', Modifiers::PUBLIC, 'A\\B');
+        $this->assertEquals('A_B_Foo', $class->getNamespacedName(true));
+        $this->assertEquals('A\\B\\Foo', $class->getNamespacedName(false));
+    }
+
+    public function testAddAndHasMethod(): void
+    {
+        $class = new ClassDef('Foo', Modifiers::PUBLIC);
+        $method = new MethodDef(Modifiers::PUBLIC, 'bar');
+
+        $this->assertFalse($class->hasMethod('bar'));
+
+        $class->addMethod($method);
+        $this->assertTrue($class->hasMethod('bar'));
+        $this->assertTrue($class->hasMethod('BAR')); // case-insensitive
+        $this->assertSame($method, $class->getMethod('bar'));
+    }
+
+    public function testGetMethodCaseInsensitive(): void
+    {
+        $class = new ClassDef('Foo', Modifiers::PUBLIC);
+        $method = new MethodDef(Modifiers::PUBLIC, 'MyMethod');
+
+        $class->addMethod($method);
+        $this->assertSame($method, $class->getMethod('mymethod'));
+        $this->assertSame($method, $class->getMethod('MYMETHOD'));
+    }
+
+    public function testHasMethodNotFound(): void
+    {
+        $class = new ClassDef('Foo', Modifiers::PUBLIC);
+        $this->assertFalse($class->hasMethod('nonexistent'));
+    }
+
+    public function testHasProperty(): void
+    {
+        $class = new ClassDef('Foo', Modifiers::PUBLIC);
+        $prop = new PropertyDef('name', Modifiers::PUBLIC, 'php::Str');
+        $class->properties['name'] = $prop;
+
+        $this->assertTrue($class->hasProperty('name'));
+        $this->assertFalse($class->hasProperty('missing'));
+        $this->assertSame($prop, $class->getProperty('name'));
+    }
+
+    public function testHasConstant(): void
+    {
+        $class = new ClassDef('Foo', Modifiers::PUBLIC);
+        $const = new ConstantDef('VERSION', Modifiers::PUBLIC, 'php::Str', '"1.0"');
+        $class->constants['VERSION'] = $const;
+
+        $this->assertTrue($class->hasConstant('VERSION'));
+        $this->assertFalse($class->hasConstant('MISSING'));
+        $this->assertSame($const, $class->getConstant('VERSION'));
+    }
+
+    public function testIsAbstract(): void
+    {
+        $abstractClass = new ClassDef('AbstractFoo', Modifiers::ABSTRACT);
+        $this->assertTrue($abstractClass->isAbstract());
+
+        $concreteClass = new ClassDef('ConcreteFoo', Modifiers::PUBLIC);
+        $this->assertFalse($concreteClass->isAbstract());
+    }
+
+    public function testRequireCtorAndEnumDefaults(): void
+    {
+        $class = new ClassDef('Foo', Modifiers::PUBLIC);
+        $this->assertFalse($class->requireCtor);
+        $this->assertFalse($class->enum);
+    }
+
+    public function testTraitAliasesAndIgnoredDefaults(): void
+    {
+        $class = new ClassDef('Foo', Modifiers::PUBLIC);
+        $this->assertEmpty($class->traitAliases);
+        $this->assertEmpty($class->traitIgnored);
+    }
+
+    public function testImplementsAndExtendsDefaults(): void
+    {
+        $class = new ClassDef('Foo', Modifiers::PUBLIC);
+        $this->assertEmpty($class->implements);
+        $this->assertEquals('', $class->extends);
+    }
+}
diff --git a/phpunit/src/Entity/ClassLikeDefTest.php b/phpunit/src/Entity/ClassLikeDefTest.php
new file mode 100644
index 00000000..10c511f2
--- /dev/null
+++ b/phpunit/src/Entity/ClassLikeDefTest.php
@@ -0,0 +1,47 @@
+<?php
+
+namespace PhpAot\Tests\Entity;
+
+use PHPUnit\Framework\TestCase;
+use PhpAot\Php\Entity\ClassLikeDef;
+use PhpAot\Php\Entity\ClassDef;
+use PhpAot\Php\Entity\InterfaceDef;
+use PhpParser\Modifiers;
+
+class ClassLikeDefTest extends TestCase
+{
+    public function testConstructWithoutNamespace(): void
+    {
+        $def = new ClassLikeDef('Foo');
+        $this->assertEquals('Foo', $def->name);
+        $this->assertEquals('', $def->namespace);
+        $this->assertEquals('', $def->extends);
+    }
+
+    public function testConstructWithNamespace(): void
+    {
+        $def = new ClassLikeDef('Foo', 'App\\Bar');
+        $this->assertEquals('Foo', $def->name);
+        $this->assertEquals('App\\Bar', $def->namespace);
+    }
+
+    public function testGetNamespacedNameWithoutNamespace(): void
+    {
+        $def = new ClassLikeDef('Foo');
+        $this->assertEquals('Foo', $def->getNamespacedName());
+        $this->assertEquals('Foo', $def->getNamespacedName(false));
+    }
+
+    public function testGetNamespacedNameSymbolic(): void
+    {
+        $def = new ClassLikeDef('Foo', 'App\\Bar');
+        // symbolic: backslashes → underscores → App_Bar_Foo
+        $this->assertEquals('App_Bar_Foo', $def->getNamespacedName(true));
+    }
+
+    public function testGetNamespacedNameNonSymbolic(): void
+    {
+        $def = new ClassLikeDef('Foo', 'App\\Bar');
+        $this->assertEquals('App\\Bar\\Foo', $def->getNamespacedName(false));
+    }
+}
diff --git a/phpunit/src/Entity/ConstantDefTest.php b/phpunit/src/Entity/ConstantDefTest.php
new file mode 100644
index 00000000..b173b9cc
--- /dev/null
+++ b/phpunit/src/Entity/ConstantDefTest.php
@@ -0,0 +1,68 @@
+<?php
+
+namespace PhpAot\Tests\Entity;
+
+use PHPUnit\Framework\TestCase;
+use PhpAot\Php\Entity\ConstantDef;
+use PhpParser\Modifiers;
+
+class ConstantDefTest extends TestCase
+{
+    public function testConstruct(): void
+    {
+        $const = new ConstantDef('MAX_SIZE', Modifiers::PUBLIC, 'php::Int', '1024L');
+
+        $this->assertEquals('MAX_SIZE', $const->name);
+        $this->assertSame(Modifiers::PUBLIC, $const->flags);
+        $this->assertEquals('php::Int', $const->type);
+        $this->assertEquals('1024L', $const->value);
+        $this->assertEquals('', $const->arrayExpr);
+        $this->assertEquals('', $const->class);
+        $this->assertNull($const->valueExpr);
+    }
+
+    public function testConstructWithStringValue(): void
+    {
+        $const = new ConstantDef('APP_NAME', Modifiers::PUBLIC, 'php::Str', 'php::Str{"MyApp"}');
+
+        $this->assertEquals('APP_NAME', $const->name);
+        $this->assertEquals('php::Str', $const->type);
+        $this->assertEquals('php::Str{"MyApp"}', $const->value);
+    }
+
+    public function testClassProperty(): void
+    {
+        $const = new ConstantDef('PI', Modifiers::PUBLIC, 'php::Float', '3.14');
+        $this->assertEquals('', $const->class);
+
+        $const->class = 'Math';
+        $this->assertEquals('Math', $const->class);
+    }
+
+    public function testArrayExprProperty(): void
+    {
+        $const = new ConstantDef('ITEMS', Modifiers::PUBLIC, 'php::Array', '[]');
+        $this->assertEquals('', $const->arrayExpr);
+
+        $const->arrayExpr = 'zval arr; array_init(&arr);';
+        $this->assertEquals('zval arr; array_init(&arr);', $const->arrayExpr);
+    }
+
+    public function testValueExprProperty(): void
+    {
+        $const = new ConstantDef('VALUE', Modifiers::PUBLIC, 'php::Int', '1L');
+        $this->assertNull($const->valueExpr);
+    }
+
+    public function testDifferentVisibilityFlags(): void
+    {
+        $publicConst = new ConstantDef('A', Modifiers::PUBLIC, 'php::Int', '1');
+        $this->assertSame(Modifiers::PUBLIC, $publicConst->flags);
+
+        $protectedConst = new ConstantDef('B', Modifiers::PROTECTED, 'php::Int', '2');
+        $this->assertSame(Modifiers::PROTECTED, $protectedConst->flags);
+
+        $privateConst = new ConstantDef('C', Modifiers::PRIVATE, 'php::Int', '3');
+        $this->assertSame(Modifiers::PRIVATE, $privateConst->flags);
+    }
+}
diff --git a/phpunit/src/Entity/FunctionDefTest.php b/phpunit/src/Entity/FunctionDefTest.php
new file mode 100644
index 00000000..7fcea0b3
--- /dev/null
+++ b/phpunit/src/Entity/FunctionDefTest.php
@@ -0,0 +1,115 @@
+<?php
+
+namespace PhpAot\Tests\Entity;
+
+use PHPUnit\Framework\TestCase;
+use PhpAot\Php\Entity\FunctionDef;
+use PhpAot\Php\ArgInfo;
+
+class FunctionDefTest extends TestCase
+{
+    public function testConstruct(): void
+    {
+        $fn = new FunctionDef('test', 'void', '');
+
+        $this->assertEquals('test', $fn->name);
+        $this->assertEquals('void', $fn->returnType);
+        $this->assertEquals('', $fn->namespace);
+        $this->assertFalse($fn->method);
+        $this->assertFalse($fn->stub);
+        $this->assertEmpty($fn->argInfoList);
+        $this->assertEquals(0, $fn->argCountRequired);
+        $this->assertEquals('', $fn->params);
+        $this->assertEquals('', $fn->returnClass);
+    }
+
+    public function testConstructWithNamespace(): void
+    {
+        $fn = new FunctionDef('run', 'php::Int', 'App\\Lib');
+
+        $this->assertEquals('run', $fn->name);
+        $this->assertEquals('php::Int', $fn->returnType);
+        $this->assertEquals('App\\Lib', $fn->namespace);
+    }
+
+    public function testGetNamespacedNameWithoutNamespace(): void
+    {
+        $fn = new FunctionDef('main', 'void', '');
+        $this->assertEquals('main', $fn->getNamespacedName());
+    }
+
+    public function testGetNamespacedNameWithNamespace(): void
+    {
+        $fn = new FunctionDef('run', 'void', 'App\\Lib');
+        $this->assertEquals('App\\Lib\\run', $fn->getNamespacedName());
+    }
+
+    public function testHasVariadicArgEmptyList(): void
+    {
+        $fn = new FunctionDef('test', 'void', '');
+        $this->assertFalse($fn->hasVariadicArg());
+    }
+
+    public function testHasVariadicArgFalse(): void
+    {
+        $fn = new FunctionDef('test', 'void', '');
+
+        $arg1 = new ArgInfo();
+        $arg1->name = 'x';
+        $arg1->type = 'php::Int';
+        $arg1->variadic = false;
+
+        $fn->argInfoList = [$arg1];
+        $this->assertFalse($fn->hasVariadicArg());
+    }
+
+    public function testHasVariadicArgTrue(): void
+    {
+        $fn = new FunctionDef('test', 'void', '');
+
+        $arg1 = new ArgInfo();
+        $arg1->name = 'args';
+        $arg1->type = 'php::Var';
+        $arg1->variadic = true;
+
+        $fn->argInfoList = [$arg1];
+        $this->assertTrue($fn->hasVariadicArg());
+    }
+
+    public function testHasVariadicArgLastOnly(): void
+    {
+        $fn = new FunctionDef('test', 'void', '');
+
+        $arg1 = new ArgInfo();
+        $arg1->name = 'x';
+        $arg1->type = 'php::Int';
+        $arg1->variadic = false;
+
+        $arg2 = new ArgInfo();
+        $arg2->name = 'rest';
+        $arg2->type = 'php::Var';
+        $arg2->variadic = true;
+
+        $fn->argInfoList = [$arg1, $arg2];
+        $this->assertTrue($fn->hasVariadicArg());
+    }
+
+    public function testMethodFlag(): void
+    {
+        $fn = new FunctionDef('handle', 'void', '');
+        $this->assertFalse($fn->method);
+
+        $fn->method = true;
+        $this->assertTrue($fn->method);
+    }
+
+    public function testParamsAndReturnClassSettable(): void
+    {
+        $fn = new FunctionDef('test', 'php::Object', '');
+        $fn->params = 'php::Int x, php::Str y';
+        $fn->returnClass = 'DateTime';
+
+        $this->assertEquals('php::Int x, php::Str y', $fn->params);
+        $this->assertEquals('DateTime', $fn->returnClass);
+    }
+}
diff --git a/phpunit/src/Entity/InterfaceDefTest.php b/phpunit/src/Entity/InterfaceDefTest.php
new file mode 100644
index 00000000..645847ff
--- /dev/null
+++ b/phpunit/src/Entity/InterfaceDefTest.php
@@ -0,0 +1,42 @@
+<?php
+
+namespace PhpAot\Tests\Entity;
+
+use PHPUnit\Framework\TestCase;
+use PhpAot\Php\Entity\InterfaceDef;
+
+class InterfaceDefTest extends TestCase
+{
+    public function testConstructWithoutNamespace(): void
+    {
+        $iface = new InterfaceDef('JsonSerializable');
+
+        $this->assertEquals('JsonSerializable', $iface->name);
+        $this->assertEquals('', $iface->namespace);
+        $this->assertEquals('', $iface->extends);
+    }
+
+    public function testConstructWithNamespace(): void
+    {
+        $iface = new InterfaceDef('Renderable', 'App\\Contracts');
+
+        $this->assertEquals('Renderable', $iface->name);
+        $this->assertEquals('App\\Contracts', $iface->namespace);
+    }
+
+    public function testGetNamespacedName(): void
+    {
+        $iface = new InterfaceDef('Logger', 'App\\Contracts');
+
+        $this->assertEquals('App_Contracts_Logger', $iface->getNamespacedName(true));
+        $this->assertEquals('App\\Contracts\\Logger', $iface->getNamespacedName(false));
+    }
+
+    public function testExtendsCanBeSet(): void
+    {
+        $iface = new InterfaceDef('Child');
+        $iface->extends = 'Parent';
+
+        $this->assertEquals('Parent', $iface->extends);
+    }
+}
diff --git a/phpunit/src/Entity/MethodDefTest.php b/phpunit/src/Entity/MethodDefTest.php
new file mode 100644
index 00000000..b050cd0b
--- /dev/null
+++ b/phpunit/src/Entity/MethodDefTest.php
@@ -0,0 +1,51 @@
+<?php
+
+namespace PhpAot\Tests\Entity;
+
+use PHPUnit\Framework\TestCase;
+use PhpAot\Php\Entity\MethodDef;
+use PhpAot\Php\Entity\FunctionDef;
+use PhpParser\Modifiers;
+
+class MethodDefTest extends TestCase
+{
+    public function testConstruct(): void
+    {
+        $method = new MethodDef(Modifiers::PUBLIC, 'handle');
+
+        $this->assertEquals('handle', $method->name);
+        $this->assertSame(Modifiers::PUBLIC, $method->flags);
+        $this->assertNull($method->functionDef);
+        $this->assertFalse($method->hasDynamicCall);
+    }
+
+    public function testGetReturnType(): void
+    {
+        $method = new MethodDef(Modifiers::PUBLIC, 'getValue');
+        $fn = new FunctionDef('getValue', 'php::Int', '');
+        $method->functionDef = $fn;
+
+        $this->assertEquals('php::Int', $method->getReturnType());
+    }
+
+    public function testGetReturnTypeVoid(): void
+    {
+        $method = new MethodDef(Modifiers::PROTECTED, 'execute');
+        $fn = new FunctionDef('execute', 'void', '');
+        $method->functionDef = $fn;
+
+        $this->assertEquals('void', $method->getReturnType());
+    }
+
+    public function testFlags(): void
+    {
+        $publicMethod = new MethodDef(Modifiers::PUBLIC, 'pub');
+        $this->assertSame(Modifiers::PUBLIC, $publicMethod->flags);
+
+        $protectedMethod = new MethodDef(Modifiers::PROTECTED, 'prot');
+        $this->assertSame(Modifiers::PROTECTED, $protectedMethod->flags);
+
+        $privateMethod = new MethodDef(Modifiers::PRIVATE, 'priv');
+        $this->assertSame(Modifiers::PRIVATE, $privateMethod->flags);
+    }
+}
diff --git a/phpunit/src/Entity/PropertyDefTest.php b/phpunit/src/Entity/PropertyDefTest.php
new file mode 100644
index 00000000..093d1bc5
--- /dev/null
+++ b/phpunit/src/Entity/PropertyDefTest.php
@@ -0,0 +1,82 @@
+<?php
+
+namespace PhpAot\Tests\Entity;
+
+use PHPUnit\Framework\TestCase;
+use PhpAot\Php\Entity\PropertyDef;
+use PhpParser\Modifiers;
+
+class PropertyDefTest extends TestCase
+{
+    public function testConstructWithDefaults(): void
+    {
+        $prop = new PropertyDef('count', Modifiers::PUBLIC, 'php::Int');
+
+        $this->assertEquals('count', $prop->name);
+        $this->assertSame(Modifiers::PUBLIC, $prop->flags);
+        $this->assertEquals('php::Int', $prop->type);
+        $this->assertNull($prop->default);
+        $this->assertFalse($prop->nullable);
+        $this->assertEquals('', $prop->class);
+    }
+
+    public function testConstructWithDefaultValue(): void
+    {
+        $prop = new PropertyDef('count', Modifiers::PUBLIC, 'php::Int', '0');
+
+        $this->assertEquals('0', $prop->default);
+    }
+
+    public function testConstructWithNullable(): void
+    {
+        $prop = new PropertyDef('name', Modifiers::PUBLIC, 'php::Str', null, true);
+
+        $this->assertTrue($prop->nullable);
+    }
+
+    public function testIsPrivate(): void
+    {
+        $privateProp = new PropertyDef('secret', Modifiers::PRIVATE, 'php::Str');
+        $this->assertTrue($privateProp->isPrivate());
+        $this->assertFalse($privateProp->isProtected());
+        $this->assertFalse($privateProp->isPublic());
+    }
+
+    public function testIsProtected(): void
+    {
+        $protectedProp = new PropertyDef('value', Modifiers::PROTECTED, 'php::Int');
+        $this->assertFalse($protectedProp->isPrivate());
+        $this->assertTrue($protectedProp->isProtected());
+        $this->assertFalse($protectedProp->isPublic());
+    }
+
+    public function testIsPublic(): void
+    {
+        $publicProp = new PropertyDef('name', Modifiers::PUBLIC, 'php::Str');
+        $this->assertFalse($publicProp->isPrivate());
+        $this->assertFalse($publicProp->isProtected());
+        $this->assertTrue($publicProp->isPublic());
+
+        // PUBLIC flag is 0, so no-flag properties are also public
+        $impliedPublic = new PropertyDef('name', 0, 'php::Str');
+        $this->assertTrue($impliedPublic->isPublic());
+    }
+
+    public function testIsStatic(): void
+    {
+        $staticProp = new PropertyDef('counter', Modifiers::PUBLIC | Modifiers::STATIC, 'php::Int');
+        $this->assertTrue($staticProp->isStatic());
+
+        $instanceProp = new PropertyDef('counter', Modifiers::PUBLIC, 'php::Int');
+        $this->assertFalse($instanceProp->isStatic());
+    }
+
+    public function testClassProperty(): void
+    {
+        $prop = new PropertyDef('data', Modifiers::PUBLIC, 'php::Var');
+        $this->assertEquals('', $prop->class);
+
+        $prop->class = 'App\\Entity\\User';
+        $this->assertEquals('App\\Entity\\User', $prop->class);
+    }
+}
diff --git a/phpunit/src/ExceptionTest.php b/phpunit/src/ExceptionTest.php
new file mode 100644
index 00000000..80d1b28d
--- /dev/null
+++ b/phpunit/src/ExceptionTest.php
@@ -0,0 +1,151 @@
+<?php
+
+namespace PhpAot\Tests;
+
+use PHPUnit\Framework\TestCase;
+use PhpAot\Php\Exception\DynamicCall;
+use PhpAot\Php\Exception\PlaceHolder;
+use PhpAot\Php\Exception\Redo;
+use PhpAot\Php\Exception\Skip;
+use PhpAot\Php\Exception\SyntaxError;
+use PhpAot\Php\Exception\TestError;
+use PhpAot\Php\Exception\Unsupported;
+use PhpAot\Php\Constants;
+
+class ExceptionTest extends TestCase
+{
+    public function testDynamicCall(): void
+    {
+        $e = new DynamicCall('Dynamic call error');
+        $this->assertInstanceOf(\RuntimeException::class, $e);
+        $this->assertEquals('Dynamic call error', $e->getMessage());
+    }
+
+    public function testPlaceHolder(): void
+    {
+        $e = new PlaceHolder('Placeholder error');
+        $this->assertInstanceOf(\RuntimeException::class, $e);
+        $this->assertEquals('Placeholder error', $e->getMessage());
+    }
+
+    public function testRedo(): void
+    {
+        $e = new Redo('Redo compilation');
+        $this->assertInstanceOf(\RuntimeException::class, $e);
+        $this->assertStringContainsString('Redo', $e->getMessage());
+    }
+
+    public function testSkip(): void
+    {
+        $e = new Skip('Skip this file');
+        $this->assertInstanceOf(\RuntimeException::class, $e);
+        $this->assertStringContainsString('Skip', $e->getMessage());
+    }
+
+    public function testSyntaxError(): void
+    {
+        $e = new SyntaxError('Unexpected token');
+        $this->assertInstanceOf(\RuntimeException::class, $e);
+        $this->assertStringContainsString('Unexpected', $e->getMessage());
+    }
+
+    public function testTestError(): void
+    {
+        $e = new TestError('Test assertion failed');
+        $this->assertInstanceOf(\RuntimeException::class, $e);
+        $this->assertStringContainsString('Test assertion', $e->getMessage());
+    }
+
+    public function testUnsupported(): void
+    {
+        $e = new Unsupported('Unsupported syntax');
+        $this->assertInstanceOf(\RuntimeException::class, $e);
+        $this->assertStringContainsString('Unsupported', $e->getMessage());
+    }
+
+    public function testCustomErrorCodes(): void
+    {
+        $e = new TestError('Error 42', 42);
+        $this->assertEquals(42, $e->getCode());
+    }
+
+    public function testCatchByBaseRuntimeException(): void
+    {
+        // All exceptions can be caught by their parent RuntimeException
+        $errors = [
+            new DynamicCall('test'),
+            new PlaceHolder('test'),
+            new Redo('test'),
+            new Skip('test'),
+            new SyntaxError('test'),
+            new TestError('test'),
+            new Unsupported('test'),
+        ];
+
+        foreach ($errors as $e) {
+            try {
+                throw $e;
+            } catch (\RuntimeException $caught) {
+                $this->assertSame($e, $caught);
+            }
+        }
+    }
+
+    public function testConstantsReservedNames(): void
+    {
+        $this->assertIsArray(Constants::CPP_RESERVED_NAMES);
+        $this->assertContains('class', Constants::CPP_RESERVED_NAMES);
+        $this->assertContains('namespace', Constants::CPP_RESERVED_NAMES);
+        $this->assertContains('int', Constants::CPP_RESERVED_NAMES);
+        $this->assertContains('void', Constants::CPP_RESERVED_NAMES);
+    }
+
+    public function testConstantsUnsupportedFunctions(): void
+    {
+        $this->assertIsArray(Constants::UNSUPPORTED_FUNCTIONS);
+        $this->assertContains('extract', Constants::UNSUPPORTED_FUNCTIONS);
+    }
+
+    public function testConstantsCompilerOptions(): void
+    {
+        $options = Constants::COMPILER_OPTIONS;
+        $this->assertIsArray($options);
+        $this->assertArrayHasKey('optimize', $options);
+        $this->assertArrayHasKey('output', $options);
+        $this->assertArrayHasKey('help', $options);
+        $this->assertArrayHasKey('debug', $options);
+        $this->assertArrayHasKey('job', $options);
+        $this->assertArrayHasKey('mode', $options);
+    }
+
+    public function testCompilerOptionOptimizeDefaults(): void
+    {
+        $opt = Constants::COMPILER_OPTIONS['optimize'];
+        $this->assertEquals('O', $opt['prefix']);
+        $this->assertIsInt($opt['defaultValue']);
+        $this->assertEquals(0, $opt['defaultValue']);
+    }
+
+    public function testCompilerOptionModeDefaults(): void
+    {
+        $opt = Constants::COMPILER_OPTIONS['mode'];
+        $this->assertEquals('bin', $opt['defaultValue']);
+    }
+
+    public function testCompilerOptionNoValueFlags(): void
+    {
+        $noValueFlags = ['help', 'version', 'no-literal-strings', 'force', 'debug', 'no-console'];
+        foreach ($noValueFlags as $flag) {
+            $this->assertArrayHasKey($flag, Constants::COMPILER_OPTIONS);
+            $this->assertTrue(Constants::COMPILER_OPTIONS[$flag]['noValue'] ?? false);
+        }
+    }
+
+    public function testMsvcSuppressedWarnings(): void
+    {
+        $warnings = Constants::MSVC_SUPPRESSED_WARNINGS;
+        $this->assertIsArray($warnings);
+        $this->assertArrayHasKey('4244', $warnings);
+        $this->assertArrayHasKey('4127', $warnings);
+    }
+}
diff --git a/phpunit/src/FileScannerTest.php b/phpunit/src/FileScannerTest.php
new file mode 100644
index 00000000..4f6a03e2
--- /dev/null
+++ b/phpunit/src/FileScannerTest.php
@@ -0,0 +1,183 @@
+<?php
+
+namespace PhpAot\Tests;
+
+use PHPUnit\Framework\TestCase;
+use PhpAot\Php\FileScanner;
+
+class FileScannerTest extends TestCase
+{
+    // ========================================================================
+    // Extension type detection
+    // ========================================================================
+
+    public function testIsPhpFile(): void
+    {
+        $this->assertTrue(FileScanner::isPhpFile('/path/to/file.php'));
+        $this->assertFalse(FileScanner::isPhpFile('/path/to/file.cc'));
+        $this->assertFalse(FileScanner::isPhpFile('/path/to/file.c'));
+        $this->assertFalse(FileScanner::isPhpFile('/path/to/file.py'));
+    }
+
+    public function testIsCppFile(): void
+    {
+        $this->assertTrue(FileScanner::isCppFile('/path/to/file.cc'));
+        $this->assertTrue(FileScanner::isCppFile('/path/to/file.cpp'));
+        $this->assertTrue(FileScanner::isCppFile('/path/to/file.cxx'));
+        $this->assertFalse(FileScanner::isCppFile('/path/to/file.c'));
+        $this->assertFalse(FileScanner::isCppFile('/path/to/file.php'));
+    }
+
+    public function testIsNativeSourceFile(): void
+    {
+        // C++ files
+        $this->assertTrue(FileScanner::isNativeSourceFile('/path/to/file.cc'));
+        $this->assertTrue(FileScanner::isNativeSourceFile('/path/to/file.cpp'));
+        $this->assertTrue(FileScanner::isNativeSourceFile('/path/to/file.cxx'));
+        // C files
+        $this->assertTrue(FileScanner::isNativeSourceFile('/path/to/file.c'));
+        // Assembly files
+        $this->assertTrue(FileScanner::isNativeSourceFile('/path/to/file.s'));
+        $this->assertTrue(FileScanner::isNativeSourceFile('/path/to/file.S'));
+        // Objective-C files
+        $this->assertTrue(FileScanner::isNativeSourceFile('/path/to/file.m'));
+        $this->assertTrue(FileScanner::isNativeSourceFile('/path/to/file.mm'));
+        // Not native source
+        $this->assertFalse(FileScanner::isNativeSourceFile('/path/to/file.php'));
+        $this->assertFalse(FileScanner::isNativeSourceFile('/path/to/file.py'));
+        $this->assertFalse(FileScanner::isNativeSourceFile('/path/to/file.h'));
+        $this->assertFalse(FileScanner::isNativeSourceFile('/path/to/file.hpp'));
+    }
+
+    // ========================================================================
+    // getFileName / getFileExt
+    // ========================================================================
+
+    public function testGetFileName(): void
+    {
+        $this->assertEquals('hello', FileScanner::getFileName('/path/to/hello.php'));
+        $this->assertEquals('helper', FileScanner::getFileName('/path/to/helper.c'));
+        $this->assertEquals('main', FileScanner::getFileName('/path/to/main.cc'));
+    }
+
+    public function testGetFileNameWithMultipleDots(): void
+    {
+        $this->assertEquals('my.test', FileScanner::getFileName('/path/to/my.test.php'));
+    }
+
+    public function testGetFileExt(): void
+    {
+        $this->assertEquals('php', FileScanner::getFileExt('/path/to/file.php'));
+        $this->assertEquals('c', FileScanner::getFileExt('/path/to/file.c'));
+        $this->assertEquals('cc', FileScanner::getFileExt('/path/to/file.cc'));
+        $this->assertEquals('S', FileScanner::getFileExt('/path/to/file.S'));
+    }
+
+    // ========================================================================
+    // Constants
+    // ========================================================================
+
+    public function testPhpExtConstant(): void
+    {
+        $this->assertEquals(['php'], FileScanner::PHP_EXT);
+    }
+
+    public function testCppExtConstant(): void
+    {
+        $this->assertContains('cc', FileScanner::CPP_EXT);
+        $this->assertContains('cpp', FileScanner::CPP_EXT);
+        $this->assertContains('cxx', FileScanner::CPP_EXT);
+    }
+
+    public function testCextConstant(): void
+    {
+        $this->assertEquals(['c'], FileScanner::C_EXT);
+    }
+
+    public function testAsmExtConstant(): void
+    {
+        $this->assertContains('s', FileScanner::ASM_EXT);
+        $this->assertContains('S', FileScanner::ASM_EXT);
+    }
+
+    public function testObjcExtConstant(): void
+    {
+        $this->assertEquals(['m'], FileScanner::OBJC_EXT);
+    }
+
+    public function testObjcxxExtConstant(): void
+    {
+        $this->assertEquals(['mm'], FileScanner::OBJCXX_EXT);
+    }
+
+    public function testNativeSrcExtConstant(): void
+    {
+        $expected = ['cpp', 'cxx', 'cc', 'c', 's', 'S', 'm', 'mm'];
+        sort($expected);
+        $actual = FileScanner::NATIVE_SRC_EXT;
+        sort($actual);
+        $this->assertEquals($expected, $actual);
+    }
+
+    // ========================================================================
+    // Scan method
+    // ========================================================================
+
+    public function testScanDirectory(): void
+    {
+        $tmpDir = sys_get_temp_dir() . '/file_scanner_test_' . uniqid();
+        mkdir($tmpDir, 0777, true);
+        mkdir($tmpDir . '/sub', 0777, true);
+
+        touch($tmpDir . '/main.php');
+        touch($tmpDir . '/helper.c');
+        touch($tmpDir . '/math.S');
+        touch($tmpDir . '/module.cc');
+        touch($tmpDir . '/lib.m');
+        touch($tmpDir . '/ignored.py');
+        touch($tmpDir . '/README.md');
+        touch($tmpDir . '/sub/nested.cpp');
+
+        $scanner = new FileScanner($tmpDir);
+        $files = $scanner->scan();
+
+        // Python and Markdown should not be included
+        $this->assertContains($tmpDir . '/main.php', $files);
+        $this->assertContains($tmpDir . '/helper.c', $files);
+        $this->assertContains($tmpDir . '/math.S', $files);
+        $this->assertContains($tmpDir . '/module.cc', $files);
+        $this->assertContains($tmpDir . '/lib.m', $files);
+        $this->assertContains($tmpDir . '/sub/nested.cpp', $files);
+        $this->assertNotContains($tmpDir . '/ignored.py', $files);
+        $this->assertNotContains($tmpDir . '/README.md', $files);
+
+        // Clean up
+        unlink($tmpDir . '/main.php');
+        unlink($tmpDir . '/helper.c');
+        unlink($tmpDir . '/math.S');
+        unlink($tmpDir . '/module.cc');
+        unlink($tmpDir . '/lib.m');
+        unlink($tmpDir . '/ignored.py');
+        unlink($tmpDir . '/README.md');
+        unlink($tmpDir . '/sub/nested.cpp');
+        rmdir($tmpDir . '/sub');
+        rmdir($tmpDir);
+    }
+
+    public function testConstructorRejectsNonexistentDir(): void
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        new FileScanner('/nonexistent/path');
+    }
+
+    public function testGetDirectory(): void
+    {
+        $tmpDir = sys_get_temp_dir() . '/file_scanner_getdir_' . uniqid();
+        mkdir($tmpDir, 0777, true);
+
+        $scanner = new FileScanner($tmpDir);
+        $this->assertEquals($tmpDir, $scanner->getDirectory());
+
+        rmdir($tmpDir);
+    }
+}
diff --git a/phpunit/src/SymbolTest.php b/phpunit/src/SymbolTest.php
new file mode 100644
index 00000000..99b3852d
--- /dev/null
+++ b/phpunit/src/SymbolTest.php
@@ -0,0 +1,71 @@
+<?php
+
+namespace PhpAot\Tests;
+
+use PHPUnit\Framework\TestCase;
+use PhpAot\Php\Symbol;
+use PhpAot\Php\CompilerBase;
+
+class SymbolTest extends TestCase
+{
+    public function testGetStaticProperty(): void
+    {
+        $this->assertEquals('php::getStaticProperty', Symbol::getStaticProperty());
+    }
+
+    public function testSetStaticProperty(): void
+    {
+        $this->assertEquals('php::setStaticProperty', Symbol::setStaticProperty());
+    }
+
+    public function testInstanceOf(): void
+    {
+        $this->assertEquals('php::instanceOf', Symbol::instanceOf());
+    }
+
+    public function testConcat(): void
+    {
+        $this->assertEquals('php::concat', Symbol::concat());
+    }
+
+    public function testConstant(): void
+    {
+        $this->assertEquals('php::constant', Symbol::constant());
+    }
+
+    public function testGetClassEntrySafe(): void
+    {
+        $this->assertEquals('php::getClassEntrySafe', Symbol::getClassEntrySafe());
+    }
+
+    public function testArgList(): void
+    {
+        $this->assertEquals('php::ArgList', Symbol::argList());
+    }
+
+    public function testGetCalledCe(): void
+    {
+        $result = Symbol::getCalledCe();
+        $this->assertStringContainsString(CompilerBase::PREFIX, $result);
+        $this->assertStringContainsString('get_called_ce', $result);
+    }
+
+    public function testGetCalledClass(): void
+    {
+        $result = Symbol::getCalledClass();
+        $this->assertStringContainsString(CompilerBase::PREFIX, $result);
+        $this->assertStringContainsString('get_called_class', $result);
+    }
+
+    public function testSafeIndex(): void
+    {
+        $result = Symbol::safeIndex('0', '10');
+        $this->assertEquals('php::safeIndex(0, 10)', $result);
+    }
+
+    public function testSafeIndexWithVariables(): void
+    {
+        $result = Symbol::safeIndex('i', 'count');
+        $this->assertEquals('php::safeIndex(i, count)', $result);
+    }
+}