feat: add backend and frontend test coverage with main-branch CI

.github/workflows/ci.yml

@@ -0,0 +1,69 @@
+name: CI
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ci-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  backend:
+    name: Backend Tests
+    runs-on: ubuntu-latest
+
+    defaults:
+      run:
+        working-directory: backend
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
+      - name: Set up uv
+        uses: astral-sh/setup-uv@v5
+
+      - name: Install backend dependencies
+        run: uv sync --group dev
+
+      - name: Run backend tests
+        run: uv run pytest
+
+  frontend:
+    name: Frontend Tests
+    runs-on: ubuntu-latest
+
+    defaults:
+      run:
+        working-directory: frontend
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: "22"
+          cache: npm
+          cache-dependency-path: frontend/package-lock.json
+
+      - name: Install frontend dependencies
+        run: npm install
+
+      - name: Run frontend tests
+        run: npm run test
+
+      - name: Run production build
+        run: npm run build

README.md

@@ -124,6 +124,28 @@ The backend and frontend need to run at the same time.
 
 ---
 
+## Running Tests
+
+Backend:
+
+```bash
+cd backend
+uv sync --group dev
+uv run pytest
+```
+
+Frontend:
+
+```bash
+cd frontend
+npm install
+npm run test
+```
+
+GitHub Actions runs these checks automatically on pushes to `main` and on pull requests that target `main`.
+
+---
+
 ## Why Developers Use This
 
 - Discover high-signal posts faster

backend/pyproject.toml

@@ -14,3 +14,13 @@ dependencies = [
     "requests>=2.34.2",
     "uvicorn>=0.48.0",
 ]
+
+[dependency-groups]
+dev = [
+    "httpx>=0.28.1",
+    "pytest>=8.4.1",
+]
+
+[tool.pytest.ini_options]
+pythonpath = ["."]
+testpaths = ["tests"]

backend/tests/test_analyzer.py

@@ -0,0 +1,25 @@
+from src.services.analyzer import PostAnalyzer
+
+
+def test_normalize_tech_stack_deduplicates_and_cleans_tokens() -> None:
+    raw = [" FastAPI ", "Python", "python", " ", "- Docker "]
+
+    result = PostAnalyzer._normalize_tech_stack(raw)
+
+    assert result == "FastAPI, Python, Docker"
+
+
+def test_normalize_tech_stack_returns_na_for_empty_values() -> None:
+    assert PostAnalyzer._normalize_tech_stack(None) == "N/A"
+    assert PostAnalyzer._normalize_tech_stack("null") == "N/A"
+
+
+def test_extract_github_url_from_text_returns_first_repo_url() -> None:
+    text = (
+        "See https://example.com first and then "
+        "https://github.com/openai/openai-python/issues/1)."
+    )
+
+    result = PostAnalyzer._extract_github_url_from_text(text)
+
+    assert result == "https://github.com/openai/openai-python/issues/1"

backend/tests/test_routes.py

@@ -0,0 +1,124 @@
+from collections.abc import Generator
+
+import pytest
+from fastapi.testclient import TestClient
+
+from src.main import app
+from src.api import routes
+
+
+@pytest.fixture
+def client() -> Generator[TestClient, None, None]:
+    with TestClient(app) as test_client:
+        yield test_client
+
+
+def test_read_root_returns_health_message(client: TestClient) -> None:
+    response = client.get("/")
+
+    assert response.status_code == 200
+    assert response.json() == {
+        "message": "Dev.to Analyzer API is running. Go to /gradio for the UI."
+    }
+
+
+def test_analyze_endpoint_returns_empty_list_when_scanner_finds_no_posts(
+    client: TestClient, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    class ScannerStub:
+        def __init__(self, tag: str) -> None:
+            self.tag = tag
+
+        def fetch_posts(self, pages: int, progress):  # noqa: ANN001
+            assert self.tag == "python"
+            assert pages == 2
+            return []
+
+    class AnalyzerStub:
+        def analyze_batch(self, posts):  # noqa: ANN001
+            raise AssertionError("Analyzer should not be called when there are no posts")
+
+    async def fake_sleep(_seconds: float) -> None:
+        return None
+
+    monkeypatch.setattr(routes, "DevToScanner", ScannerStub)
+    monkeypatch.setattr(routes, "PostAnalyzer", AnalyzerStub)
+    monkeypatch.setattr(routes.asyncio, "sleep", fake_sleep)
+
+    response = client.get("/api/analyze", params={"tag": "python", "pages": 2})
+
+    assert response.status_code == 200
+    assert response.json() == []
+
+
+def test_analyze_endpoint_transforms_scanner_and_analyzer_output(
+    client: TestClient, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    raw_posts = [
+        {
+            "id": 101,
+            "title": "Async API Patterns",
+            "published_at": "2026-07-08T12:00:00Z",
+            "public_reactions_count": 12,
+            "comments_count": 3,
+            "url": "https://dev.to/example/async-api-patterns",
+            "user": {
+                "name": "Ada Lovelace",
+                "profile_image_90": "https://images.dev/avatar.png",
+            },
+        }
+    ]
+
+    class ScannerStub:
+        def __init__(self, tag: str) -> None:
+            self.tag = tag
+
+        def fetch_posts(self, pages: int, progress):  # noqa: ANN001
+            assert self.tag == "fastapi"
+            assert pages == 1
+            progress(1.0, desc="stub")
+            return [post.copy() for post in raw_posts]
+
+        def get_post_details(self, post_id: int) -> str:
+            assert post_id == 101
+            return "Body markdown with https://github.com/acme/project"
+
+    class AnalyzerStub:
+        def analyze_batch(self, posts):  # noqa: ANN001
+            assert posts[0]["body_markdown"] == "Body markdown with https://github.com/acme/project"
+            return [
+                {
+                    "id": 101,
+                    "tech_stack": "FastAPI, Python",
+                    "pain_point": "Blocking requests slowed the API.",
+                    "solution": "Move IO to async endpoints.",
+                    "github_url": "https://github.com/acme/project",
+                }
+            ]
+
+    async def fake_sleep(_seconds: float) -> None:
+        return None
+
+    monkeypatch.setattr(routes, "DevToScanner", ScannerStub)
+    monkeypatch.setattr(routes, "PostAnalyzer", AnalyzerStub)
+    monkeypatch.setattr(routes.asyncio, "sleep", fake_sleep)
+
+    response = client.get("/api/analyze", params={"tag": "fastapi", "pages": 1})
+
+    assert response.status_code == 200
+    assert response.json() == [
+        {
+            "id": 101,
+            "author": "Ada Lovelace",
+            "avatar": "https://images.dev/avatar.png",
+            "date": "2026-07-08",
+            "topic": "Async API Patterns",
+            "tech_stack": "FastAPI, Python",
+            "problem": "Blocking requests slowed the API.",
+            "solution": "Move IO to async endpoints.",
+            "github_url": "https://github.com/acme/project",
+            "reacts": 12,
+            "comments": 3,
+            "url": "https://dev.to/example/async-api-patterns",
+        }
+    ]

frontend/app/page.test.tsx

@@ -0,0 +1,69 @@
+import { render, screen, waitFor } from "@testing-library/react"
+import userEvent from "@testing-library/user-event"
+
+import DevToAnalyzer from "./page"
+
+
+const apiResult = [
+  {
+    id: 1,
+    author: "Grace Hopper",
+    avatar: "https://images.dev/grace.png",
+    date: "2026-07-08",
+    topic: "Ship Better Python APIs",
+    tech_stack: "FastAPI, Python",
+    problem: "Slow sync handlers.",
+    solution: "Adopt async IO.",
+    github_url: "https://github.com/acme/api",
+    reacts: 14,
+    comments: 2,
+    url: "https://dev.to/example/post",
+  },
+]
+
+describe("DevToAnalyzer page", () => {
+  afterEach(() => {
+    vi.restoreAllMocks()
+  })
+
+  it("fetches analysis results with the selected filters", async () => {
+    const user = userEvent.setup()
+    const fetchMock = vi.fn().mockResolvedValue({
+      ok: true,
+      json: async () => apiResult,
+    })
+    vi.stubGlobal("fetch", fetchMock)
+
+    render(<DevToAnalyzer />)
+
+    await user.clear(screen.getByPlaceholderText("e.g. webdev, python, react"))
+    await user.type(screen.getByPlaceholderText("e.g. webdev, python, react"), "fastapi")
+    await user.clear(screen.getByRole("spinbutton"))
+    await user.type(screen.getByRole("spinbutton"), "4")
+    await user.click(screen.getByRole("button", { name: "Analyze Posts" }))
+
+    await waitFor(() =>
+      expect(fetchMock).toHaveBeenCalledWith(
+        "http://127.0.0.1:8000/api/analyze?tag=fastapi&pages=4"
+      )
+    )
+    expect((await screen.findAllByText("Grace Hopper")).length).toBeGreaterThan(0)
+    expect(screen.getByRole("link", { name: "Repo" })).toHaveAttribute(
+      "href",
+      "https://github.com/acme/api"
+    )
+  })
+
+  it("shows an error message when the API request fails", async () => {
+    const user = userEvent.setup()
+    const consoleErrorSpy = vi.spyOn(console, "error").mockImplementation(() => {})
+    vi.stubGlobal("fetch", vi.fn().mockResolvedValue({ ok: false }))
+
+    render(<DevToAnalyzer />)
+
+    await user.click(screen.getByRole("button", { name: "Analyze Posts" }))
+
+    expect(await screen.findByText("Failed to fetch data from API")).toBeInTheDocument()
+    expect(consoleErrorSpy).toHaveBeenCalled()
+  })
+})

frontend/components/analyzer/results-section.test.tsx

@@ -0,0 +1,63 @@
+import { render, screen } from "@testing-library/react"
+import userEvent from "@testing-library/user-event"
+
+import { ResultsSection, type PostData } from "./results-section"
+
+
+const data: PostData[] = [
+  {
+    id: 1,
+    author: "Grace Hopper",
+    avatar: "https://images.dev/grace.png",
+    date: "2026-07-08",
+    topic: "Ship Better Python APIs",
+    tech_stack: "FastAPI, Python",
+    problem: "Slow sync handlers.",
+    solution: "Adopt async IO.",
+    github_url: "https://github.com/acme/api",
+    reacts: 14,
+    comments: 2,
+    url: "https://dev.to/example/post",
+  },
+]
+
+describe("ResultsSection", () => {
+  afterEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it("copies a readable text summary to the clipboard", async () => {
+    const user = userEvent.setup()
+    const writeTextMock = vi.mocked(navigator.clipboard.writeText)
+
+    render(<ResultsSection data={data} />)
+
+    await user.click(screen.getByRole("button", { name: /copy data/i }))
+
+    expect(writeTextMock).toHaveBeenCalledWith(
+      expect.stringContaining("Grace Hopper - Ship Better Python APIs")
+    )
+    expect(writeTextMock).toHaveBeenCalledWith(
+      expect.stringContaining("GitHub URL: https://github.com/acme/api")
+    )
+  })
+
+  it("exports the current results as csv", async () => {
+    const user = userEvent.setup()
+    const createObjectURLMock = vi.mocked(URL.createObjectURL)
+    const revokeObjectURLMock = vi.mocked(URL.revokeObjectURL)
+    const clickSpy = vi
+      .spyOn(HTMLAnchorElement.prototype, "click")
+      .mockImplementation(() => {})
+
+    render(<ResultsSection data={data} />)
+
+    await user.click(screen.getByRole("button", { name: /export csv/i }))
+
+    expect(createObjectURLMock).toHaveBeenCalledTimes(1)
+    const blob = createObjectURLMock.mock.calls[0][0] as Blob
+    await expect(blob.text()).resolves.toContain('"Grace Hopper"')
+    expect(clickSpy).toHaveBeenCalledTimes(1)
+    expect(revokeObjectURLMock).toHaveBeenCalledWith("blob:mock-url")
+  })
+})