[Test] Improve HTTP Server Test Coverage For /metrics And Count Endpoints

• With count=3 and seed=1, expect a JSON array length of 3 containing seededFace(1), seededFace(2), and seededFace(3).
• Verify a status of 200, an application/json Content-Type, and a CORS header *.

4. Error Handling for Invalid Count

• When count is non-numeric (e.g., 'abc') with Accept: application/json, expect a 400 status and a JSON error object { error: 'Invalid count: abc' }.
• When count is non-numeric without the Accept header, expect a 400 status, a text/plain Content-Type, and an error message 'Invalid count: abc'.

How to Apply

To apply these changes, modify tests/unit/server.test.js in place:

• After existing tests, append the new test cases using the established makeRequest helper.
• Use the existing FACES array and seededFace import to validate outputs.

How to Verify

To verify that the new HTTP server tests pass, run npm test or npm run test and ensure that all new tests pass, confirming coverage for the /metrics and count endpoints.

Implementation

Here's an example implementation of the new test cases in tests/unit/server.test:

describe('HTTP Server Tests', () => {
  // ... existing tests ...

  describe('/metrics endpoint', () => {
    it('should return 200 status code', async () => {
      const response = await makeRequest('/metrics');
      expect(response.status).toBe(200);
    });

    it('should return text/plain; version=0.0.4 Content-Type header', async () => {
      const response = await makeRequest('/metrics');
      expect(response.headers['content-type']).toBe('text/plain; version=0.0.4');
    });

    it('should return * Access-Control-Allow-Origin header', async () => {
      const response = await makeRequest('/metrics');
      expect(response.headers['access-control-allow-origin']).toBe('*');
    });

    it('should return metric lines for counters', async () => {
      const response = await makeRequest('/metrics');
      const metricLines = response.body.split('\n');
      expect(metricLines).toContain('emoticon_requests_total');
      expect(metricLines).toContain('emoticon_requests_root_total');
    });
  });

  describe('/json?count=<n> endpoint', () => {
    it('should return 200 status code with count=3', async () => {
      const response = await makeRequest('/json?count=3');
      expect(response.status).toBe(200);
    });

    it('should return application/json header with count=3', async () => {
      const response = await makeRequest('/json?count=3');
      expect(response.headers['content-type']).toBe('application/json');
    });

    it('should return JSON array of length 3 with count=3', async () => {
      const response = await makeRequest('/json?count=3');
      const jsonArray = JSON.parse(response.body);
      expect(jsonArray.length).toBe(3);
    });

    it('should return CORS header * with count=3', async () => {
      const response = await makeRequest('/json?count=3');
      expect(response.headers['access-control-allow-origin']).toBe('*');
    });
  });

  describe('/json?count=<n>&seed=<s> endpoint', () => {
    it('should return 200 status code with count=3 and seed=1', async () => {
      const response = await makeRequest('/json?count=3&seed=1');
      expect(response.status).toBe(200);
    });

    it('should return application/json header with count=3 and seed=1', async () => {
      const response = await makeRequest('/json?count=3&seed=1');
      expect(response.headers['content-type']).toBe('application/json');
    });

    it('should return JSON array of length 3 containing seededFace(1), seededFace(2), seededFace(3) with count=3 and seed=1', async () => {
      const response = await makeRequest('/json?count=3&seed=1');
      const jsonArray = JSON.parse(response.body);
      expect(jsonArray.length).toBe(3);
      expect(jsonArray).toContain(seededFace(1));
      expect(jsonArray).toContain(seededFace(2));
      expect(jsonArray).toContain(seededFace(3));
    });

    it('should return CORS header * with count=3 and seed=1', async () => {
      const response = await make('/json?count=3&seed=1');
      expect(response.headers['access-control-allow-origin']).toBe('*');
    });
  });

  describe('Error handling for invalid count', () => {
    it('should return 400 status with non-numeric count and application/json Accept header', async () => {
      const response = await makeRequest('/json?count=abc', { headers: { accept: 'application/json' } });
      expect(response.status).toBe(400);
    });

    it('should return JSON error object with non-numeric count and application/json Accept header', async () => {
      const response = await makeRequest('/json?count=abc', { headers: { accept: 'application/json' } });
      const errorObject = JSON.parse(response.body);
      expect(errorObject.error).toBe('Invalid count: abc');
    });

    it('should return 400 status with non-numeric count without Accept header', async () => {
      const response = await makeRequest('/json?count=abc');
      expect(response.status).toBe(400);
    });

    it('should return text/plain Content-Type header with non-numeric count without Accept header', async () => {
      const response = await makeRequest('/json?count=abc');
      expect(response.headers['content-type']).toBe('text/plain');
    });

    it('should return error message with non-numeric count without Accept header', async () => {
      const response = await makeRequest('/json?count=abc');
      const errorMessage = response.body;
      expect(errorMessage).toBe('Invalid count: abc');
    });
  });
});

Q: What is the purpose of improving test coverage for the /metrics and count endpoints?

A: Ensuring comprehensive test coverage is crucial for maintaining the reliability and stability of software applications. In the context of HTTP servers, testing core endpoints is essential, but it's equally important to cover key functionality such as Prometheus metrics and JSON count support. This lack of test coverage can lead to regressions and decreased confidence in core functionality.

Q: What are the current test coverage limitations for the /metrics and count endpoints?

A: The current HTTP server tests in tests/unit/server.test.js cover core endpoints such as /version, /, /list, /json, /health, and 404 paths. However, these tests omit key functionality, including the Prometheus metrics endpoint and JSON count support for both simple and seeded scenarios.

Q: What are the desired changes to improve test coverage for the /metrics and count endpoints?

A: To address this issue, we need to update tests/unit/server.test.js to include the following high-impact test cases:

• GET /metrics: Send a GET request to /metrics. Expect a status code of 200. Expect the Content-Type header to match text/plain; version=0.0.4. Expect the Access-Control-Allow-Origin header to be *. Verify that the response body includes metric lines for counters (e.g., 'emoticon_requests_total', 'emoticon_requests_root_total', etc.).
• GET /json?count=: With count=3, expect a status of 200 and an application/json header. Expect a JSON array of length 3, each item matching one of the built-in FACES. Verify that the CORS header * is present.
• GET /json?count=&seed=: With count=3 and seed=1, expect a JSON array length of 3 containing seededFace(1), seededFace(2), and seededFace(3). Verify a status of 200, an application/json Content-Type, and a CORS header *.
• Error handling for invalid count: When count is non-numeric (e.g., 'abc') with Accept: application/json, expect a 400 status and a JSON error object { error: 'Invalid count: abc' }. When count is non-numeric without the Accept header, expect a 400 status, a text/plain Content-Type, and an error message 'Invalid count: abc'.