1. Introduction
Behavior-Driven Development (BDD) is an agile software development approach that encourages collaboration among developers, QA, and non-technical participants in a software project. Mockito offers BDDMockito which is a BDD-style variant of its typical mocking API. This API is more in line with the "Given, When, Then" style of writing specifications in BDD.
2. Example Steps
1. Define a sample service to be tested.
2. Use the BDDMockito API to write BDD-style tests for the service.
3. Demonstrate the usage of given(), willThrow(), and willReturn() methods from BDDMockito.
4. Run the tests and observe the output.
3. Mockito BDDMockito Example
// Step 1: Define a sample service
class SampleService {
String processData(String input) {
return "Processed: " + input;
}
}
// Step 2: Use the BDDMockito API to write BDD-style tests
import org.junit.jupiter.api.Test;
import static org.mockito.BDDMockito.*;
public class SampleServiceTest {
@Test
public void testProcessData() {
// Mock the SampleService using BDDMockito
SampleService mockService = mock(SampleService.class);
// Given: Set up the mock behavior
given(mockService.processData("rawData")).willReturn("Mocked: rawData");
// When: Call the method
String result = mockService.processData("rawData");
// Then: Assert and print the result
System.out.println(result);
// Given: Set up the mock to throw an exception
given(mockService.processData("exceptionData")).willThrow(new RuntimeException("Exception occurred"));
// When: Calling the method which throws an exception
try {
mockService.processData("exceptionData");
} catch (RuntimeException ex) {
// Then: Print the exception
System.out.println(ex.getMessage());
}
}
}
Output:
Mocked: rawData Exception occurred
4. Step By Step Explanation
1. We have a simple SampleService with a processData method that appends "Processed:" to the provided input.
2. In SampleServiceTest, using BDDMockito, we mock the SampleService.
3. The given() method is BDDMockito's replacement for Mockito's when(). We use it to specify a condition, i.e., when processData("rawData") is called on the mock, then it should return "Mocked: rawData".
4. We demonstrate the usage of willReturn() to stub the desired method return value.
5. Another demonstration is done using willThrow() where we specify that calling processData("exceptionData") should throw a RuntimeException.
6. The results align with our mock setup, showcasing the power and elegance of BDDMockito in writing BDD-style tests.