test(problems): Add comprehensive tests for problem controller functions

- Added tests for `getIndex` to ensure the problem generator index is returned successfully.
- Mocked `problemGenerator` in the test suite for `generateProblem`.
- Tested the successful generation of a problem with the `generateProblem` function.
- Added test cases to handle generator not found (404) and internal server errors (500) for `generateProblem`.
- Ensured proper response validation for all scenarios.

tests/controllers/problemController.test.js

@@ -0,0 +1,97 @@
+/**
+ * @file tests/controllers/problemController.test.js
+ * @description Tests for problem controller.
+ */
+
+const problemController = require("../../src/controllers/problemController");
+const problemGenerator = require("../../src/problem-generators");
+const index = require("../../src/problem-generators/index.json");
+
+jest.mock("../../src/problem-generators");
+
+describe("ProblemController - getIndex", () => {
+  it("should return the problem generator index successfully", () => {
+    const req = {};
+    const res = {
+      success: jest.fn(),
+    };
+
+    problemController.getIndex(req, res);
+
+    expect(res.success).toHaveBeenCalledWith(
+      index,
+      "Problem generator index retrieved successfully."
+    );
+  });
+});
+
+describe("ProblemController - generateProblem", () => {
+  it("should generate a problem successfully", () => {
+    const req = {
+      params: { 0: "topic1/topic2" },
+      query: { options: "someOptions" },
+    };
+    const res = {
+      success: jest.fn(),
+      notFound: jest.fn(),
+      internalServerError: jest.fn(),
+    };
+    const generatedProblem = { problem: "generatedProblem" };
+    problemGenerator.prototype.generateOne.mockReturnValue(generatedProblem);
+
+    problemController.generateProblem(req, res);
+
+    expect(problemGenerator.prototype.generateOne).toHaveBeenCalledWith({
+      path: ["topic1", "topic2"],
+      options: "someOptions",
+    });
+    expect(res.success).toHaveBeenCalledWith(
+      generatedProblem,
+      "Problem generated successfully."
+    );
+  });
+
+  it("should return 404 if generator is not found", () => {
+    const req = {
+      params: { 0: "invalidTopic" },
+      query: { options: "someOptions" },
+    };
+    const res = {
+      success: jest.fn(),
+      notFound: jest.fn(),
+      internalServerError: jest.fn(),
+    };
+    problemGenerator.prototype.generateOne.mockImplementation(() => {
+      throw new Error("Generator not found");
+    });
+
+    problemController.generateProblem(req, res);
+
+    expect(res.notFound).toHaveBeenCalledWith(
+      "Generator not found.",
+      "GENERATOR_NOT_FOUND"
+    );
+  });
+
+  it("should return 500 if there is an error generating the problem", () => {
+    const req = {
+      params: { 0: "topic1/topic2" },
+      query: { options: "someOptions" },
+    };
+    const res = {
+      success: jest.fn(),
+      notFound: jest.fn(),
+      internalServerError: jest.fn(),
+    };
+    problemGenerator.prototype.generateOne.mockImplementation(() => {
+      throw new Error("Some other error");
+    });
+
+    problemController.generateProblem(req, res);
+
+    expect(res.internalServerError).toHaveBeenCalledWith(
+      "Error generating problem.",
+      "GENERATE_PROBLEM_ERROR"
+    );
+  });
+});