Save original value in FalseyValue

src/Spies/FalseyValue.php

@@ -4,4 +4,11 @@
 
 // A special case for falsey return values
 class FalseyValue {
+	public function __construct( $value ) {
+		$this->value = $value;
+	}
+
+	public function get_value() {
+		return $this->value;
+	}
 }

src/Spies/GlobalSpies.php

@@ -127,7 +127,7 @@ private static function replace_global_function( $function_name ) {
 
 	private static function filter_return_for( $return ) {
 		if ( $return instanceof FalseyValue ) {
-			return null;
+			return $return->get_value();
 		}
 		return $return;
 	}

src/Spies/Spy.php

@@ -215,9 +215,9 @@ public function that_returns( $value ) {
 	 * @return Spy This Spy
 	 */
 	public function and_return( $value ) {
-		// Add a special case for falsey return values
+		// Add a special case for falsey return values so we can detect them
 		if ( ! $value ) {
-			$value = new FalseyValue();
+			$value = new FalseyValue( $value );
 		}
 		if ( isset( $this->with_arguments ) ) {
 			$this->conditional_returns[] = [ 'args' => $this->with_arguments, 'return' => $value ];
@@ -410,8 +410,8 @@ private function filter_return_for( $return, $args, $options = [] ) {
 		if ( is_callable( $return ) ) {
 			return call_user_func_array( $return, $args );
 		}
-		if ( $return instanceof FalseyValue && ! $options['return_falsey_objects'] ) {
-			return null;
+		if ( $return instanceof FalseyValue && empty( $options['return_falsey_objects'] ) ) {
+			return $return->get_value();
 		}
 		return $return;
 	}

tests/SpyTest.php

@@ -263,6 +263,11 @@ public function test_stub_on_internal_existing_method_replaces_return_value_of_e
 		$this->assertEquals( 'boo', trigger_error( 'foo' ) );
 	}
 
+	public function test_stub_on_internal_existing_method_replaces_return_value_of_existing_method_if_empty() {
+		\Spies\mock_function( 'trigger_error' )->and_return( [] );
+		$this->assertEquals( [], trigger_error( 'foo' ) );
+	}
+
 	public function test_stub_on_internal_existing_method_replaces_return_value_of_existing_method_if_null() {
 		\Spies\mock_function( 'trigger_error' )->and_return( null );
 		$this->assertEquals( null, trigger_error( 'foo' ) );