Verify advanced data source processes complex data correctly

Preconditions (2)

Step 1: Create an instance of AdvancedDataSource

Step 2: Provide a complex data input (e.g., nested JSON or structured object)

Step 3: Call the processData method with the complex data

Step 4: Capture the output result

Step 5: Verify the output matches the expected processed result

✅ Expected Result: The processData method returns the correctly processed output for the complex data input

Automation Requirements - JUnit 5

Assertions Needed:

Assert that the output is not null

Assert that the output matches the expected processed data

Best Practices:

Use @BeforeEach to set up test data

Use descriptive test method names

Keep tests independent and repeatable

Use assertions from org.junit.jupiter.api.Assertions

Automated Solution

JUnit

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;

class AdvancedDataSourceTest {

    private AdvancedDataSource dataSource;
    private String complexDataInput;
    private String expectedOutput;

    @BeforeEach
    void setUp() {
        dataSource = new AdvancedDataSource();
        // Example complex data as JSON string
        complexDataInput = "{\"user\":{\"id\":123,\"name\":\"Alice\"},\"items\":[1,2,3]}";
        // Expected processed output (example)
        expectedOutput = "Processed: user Alice with 3 items";
    }

    @Test
    void testProcessComplexData() {
        String result = dataSource.processData(complexDataInput);
        assertNotNull(result, "Result should not be null");
        assertEquals(expectedOutput, result, "Processed output should match expected");
    }
}

// Dummy AdvancedDataSource class for context
class AdvancedDataSource {
    public String processData(String data) {
        // Simulate processing complex data
        if (data.contains("Alice") && data.contains("items")) {
            return "Processed: user Alice with 3 items";
        }
        return "";
    }
}

This test class AdvancedDataSourceTest uses JUnit 5 to automate the manual test case.

We use @BeforeEach to set up the test data before each test runs. This keeps tests clean and repeatable.

The test method testProcessComplexData calls the processData method with a complex JSON string as input.

We assert that the result is not null and that it exactly matches the expected processed output string.

This ensures the advanced data source handles complex data correctly.

Common Mistakes - 4 Pitfalls

Not initializing test data before each test

Using assertEquals with incorrect expected value

Not checking for null result before other assertions

Mixing JUnit 4 and JUnit 5 annotations and assertions

Bonus Challenge

Now add data-driven testing with 3 different complex data inputs and expected outputs

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