Test Generation Skill

When generating tests, follow this process:

1. Analyze the Target

• Read the source code thoroughly before writing any tests.
• Identify the public API surface: exports, parameters, return types.
• Map dependencies that need mocking or stubbing.
• List the behavioral contracts: what must always be true?

2. Plan Test Cases

Organize tests into categories:

Happy Path

• Standard inputs produce expected outputs.
• All documented use cases work correctly.

Edge Cases

• Empty inputs (null, undefined, empty string, empty array, 0).
• Boundary values (min/max integers, very long strings, single-element arrays).
• Unicode and special characters in string inputs.

Error Cases

• Invalid input types and shapes.
• Missing required fields.
• Network/IO failures (timeouts, connection refused, permission denied).
• Concurrent access and race conditions where applicable.

Integration Points

• Verify correct interaction with dependencies.
• Check that mocks match the real interface.
• Test retry and fallback behavior.

3. Write Tests

Follow these conventions:

describe("ModuleName", () => {
  describe("functionName", () => {
    it("should [expected behavior] when [condition]", () => {
      // Arrange — set up inputs and mocks
      // Act — call the function
      // Assert — verify the result
    });
  });
});

Mocking Strategy

• Mock at the boundary (network, filesystem, database), not internal functions.
• Use dependency injection where possible instead of module mocking.
• Verify mock call counts and arguments, not just return values.
• Reset mocks between tests to prevent state leakage.

Assertions

• Assert on specific values, not just truthiness.
• Check error messages and types, not just that an error was thrown.
• Use snapshot tests sparingly — only for stable, complex output.
• Verify side effects (files written, events emitted, logs produced).

4. Quality Checks

Before finalizing:

• Run the tests and confirm they pass.
• Verify each test fails when the behavior it tests is broken.
• Check that tests are independent and can run in any order.
• Ensure test names describe the behavior, not the implementation.
• Remove any redundant tests that don’t add coverage.