How does ArgumentCaptor handle complex objects differently when using getValue() versus getAllValues()

Handling Complex Objects with `getValue()`

- Single Invocation: When a method is invoked only once, `getValue()` is used to retrieve the captured argument. This method returns the last captured value if the method is called multiple times, which might not be ideal for complex objects if you need to verify all invocations.

Example:

java
  @Test
  void testComplexObject() {
      // Arrange
      MyService service = mock(MyService.class);
      MyObject expectedObject = new MyObject("data");
      
      // Act
      service.process(expectedObject);
      
      // Capture
      ArgumentCaptor captor = ArgumentCaptor.forClass(MyObject.class);
      verify(service).process(captor.capture());
      
      // Assert
      MyObject capturedObject = captor.getValue();
      assertEquals("data", capturedObject.getData());
  }
  

- Complexity: When dealing with complex objects, `getValue()` will return the last object captured. This can be sufficient if you only need to verify the last invocation or if the method is called once. However, if the method is invoked multiple times with different complex objects, using `getValue()` alone might not be enough.

Handling Complex Objects with `getAllValues()`

- Multiple Invocations: If a method is called multiple times, `getAllValues()` is more suitable for capturing and asserting all the arguments passed. This method returns a list of all captured arguments in the order they were invoked.

Example:

java
  @Test
  void testMultipleComplexObjects() {
      // Arrange
      MyService service = mock(MyService.class);
      MyObject obj1 = new MyObject("data1");
      MyObject obj2 = new MyObject("data2");
      
      // Act
      service.process(obj1);
      service.process(obj2);
      
      // Capture
      ArgumentCaptor captor = ArgumentCaptor.forClass(MyObject.class);
      verify(service, times(2)).process(captor.capture());
      
      // Assert
      List capturedObjects = captor.getAllValues();
      assertEquals("data1", capturedObjects.get(0).getData());
      assertEquals("data2", capturedObjects.get(1).getData());
  }
  

- Complexity: When using `getAllValues()` with complex objects, you can verify each object individually. This is particularly useful when the method is called multiple times with different arguments, allowing you to assert each captured object's properties.

Key Differences

- Invocation Count: `getValue()` is suitable for single invocations or when you only need the last captured value. `getAllValues()` is necessary when the method is called multiple times, as it returns all captured arguments.

- Assertion Granularity: With `getValue()`, you can only assert the last captured value. Using `getAllValues()` allows you to assert each captured argument individually, providing more granular control over your assertions.

In summary, when handling complex objects with `ArgumentCaptor`, `getValue()` is best for single invocations or when only the last argument matters, while `getAllValues()` is ideal for multiple invocations, allowing you to verify each captured argument individually.