test: add comprehensive unit tests for 80% coverage

Add unit tests for core modules:
- analyzers: commits, issues, pull_requests, productivity
- api: client, models
- cli: output formatting
- core: exceptions
- exporters: csv_exporter

Coverage improved from 54% to 80% with 236 passing tests.

Author: amargiovanni

tests/unit/analyzers/test_commits.py

@@ -0,0 +1,185 @@
+"""Tests for commit analyzer."""
+
+import pytest
+from datetime import datetime, timezone
+from unittest.mock import Mock, MagicMock
+
+from src.github_analyzer.analyzers.commits import CommitAnalyzer
+from src.github_analyzer.api.models import Commit
+from src.github_analyzer.config.validation import Repository
+
+
+class TestCommitAnalyzerInit:
+    """Tests for CommitAnalyzer initialization."""
+
+    def test_initializes_with_client(self):
+        """Test analyzer initializes with client."""
+        client = Mock()
+        analyzer = CommitAnalyzer(client)
+        assert analyzer._client is client
+
+
+class TestCommitAnalyzerFetchAndAnalyze:
+    """Tests for fetch_and_analyze method."""
+
+    def test_fetches_commits_from_api(self):
+        """Test fetches commits from GitHub API."""
+        client = Mock()
+        client.paginate.return_value = []
+        client.get.return_value = None
+
+        analyzer = CommitAnalyzer(client)
+        repo = Repository(owner="test", name="repo")
+        since = datetime.now(timezone.utc)
+
+        result = analyzer.fetch_and_analyze(repo, since)
+
+        client.paginate.assert_called_once()
+        assert result == []
+
+    def test_processes_commits_into_objects(self):
+        """Test processes raw commits into Commit objects."""
+        raw_commit = {
+            "sha": "abc123def456",
+            "commit": {
+                "author": {
+                    "name": "Test Author",
+                    "email": "test@example.com",
+                    "date": "2025-01-15T10:00:00Z",
+                },
+                "message": "Test commit message",
+            },
+            "author": {"login": "testuser"},
+            "committer": {"login": "testuser"},
+            "stats": {"additions": 10, "deletions": 5, "total": 15},
+            "files": [{"filename": "test.py"}],
+            "html_url": "https://github.com/test/repo/commit/abc123",
+        }
+
+        client = Mock()
+        client.paginate.return_value = [{"sha": "abc123def456"}]
+        client.get.return_value = raw_commit
+
+        analyzer = CommitAnalyzer(client)
+        repo = Repository(owner="test", name="repo")
+        since = datetime.now(timezone.utc)
+
+        result = analyzer.fetch_and_analyze(repo, since)
+
+        assert len(result) == 1
+        assert isinstance(result[0], Commit)
+        assert result[0].sha == "abc123def456"
+        assert result[0].author_login == "testuser"
+
+    def test_handles_missing_commit_details(self):
+        """Test handles when commit details fetch returns None."""
+        client = Mock()
+        # Return a commit with sha but no details
+        client.paginate.return_value = [{"sha": "abc123def456"}]
+        client.get.return_value = None
+
+        analyzer = CommitAnalyzer(client)
+        repo = Repository(owner="test", name="repo")
+        since = datetime.now(timezone.utc)
+
+        result = analyzer.fetch_and_analyze(repo, since)
+        # Should still create commit from basic data
+        assert len(result) == 1
+
+    def test_fetches_details_for_each_commit(self):
+        """Test fetches details for each commit."""
+        raw_detail = {
+            "sha": "valid123def456",
+            "commit": {"author": {"date": "2025-01-15T10:00:00Z"}, "message": "test"},
+            "author": {"login": "user"},
+            "committer": {"login": "user"},
+            "stats": {"additions": 10, "deletions": 5},
+            "files": [],
+        }
+
+        client = Mock()
+        client.paginate.return_value = [{"sha": "valid123def456"}]
+        client.get.return_value = raw_detail
+
+        analyzer = CommitAnalyzer(client)
+        repo = Repository(owner="test", name="repo")
+        since = datetime.now(timezone.utc)
+
+        result = analyzer.fetch_and_analyze(repo, since)
+
+        assert len(result) == 1
+        assert client.get.called
+
+
+class TestCommitAnalyzerGetStats:
+    """Tests for get_stats method."""
+
+    def test_returns_empty_stats_for_no_commits(self):
+        """Test returns zeros for empty commit list."""
+        client = Mock()
+        analyzer = CommitAnalyzer(client)
+
+        stats = analyzer.get_stats([])
+
+        assert stats["total"] == 0
+        assert stats["merge_commits"] == 0
+        assert stats["revert_commits"] == 0
+        assert stats["total_additions"] == 0
+        assert stats["total_deletions"] == 0
+        assert stats["unique_authors"] == 0
+
+    def test_calculates_correct_stats(self):
+        """Test calculates correct statistics."""
+        client = Mock()
+        analyzer = CommitAnalyzer(client)
+
+        commits = [
+            Commit(
+                repository="test/repo",
+                sha="abc123def456",
+                author_login="user1",
+                author_email="user1@test.com",
+                committer_login="user1",
+                date=datetime.now(timezone.utc),
+                message="feat: add feature",
+                full_message="feat: add feature",
+                additions=100,
+                deletions=50,
+                files_changed=5,
+            ),
+            Commit(
+                repository="test/repo",
+                sha="def456ghi789",
+                author_login="user2",
+                author_email="user2@test.com",
+                committer_login="user2",
+                date=datetime.now(timezone.utc),
+                message="Merge pull request #1",
+                full_message="Merge pull request #1",
+                additions=20,
+                deletions=10,
+                files_changed=2,
+            ),
+            Commit(
+                repository="test/repo",
+                sha="ghi789jkl012",
+                author_login="user1",
+                author_email="user1@test.com",
+                committer_login="user1",
+                date=datetime.now(timezone.utc),
+                message="Revert \"feat: add feature\"",
+                full_message="Revert \"feat: add feature\"",
+                additions=50,
+                deletions=100,
+                files_changed=5,
+            ),
+        ]
+
+        stats = analyzer.get_stats(commits)
+
+        assert stats["total"] == 3
+        assert stats["merge_commits"] == 1
+        assert stats["revert_commits"] == 1
+        assert stats["total_additions"] == 170
+        assert stats["total_deletions"] == 160
+        assert stats["unique_authors"] == 2

tests/unit/analyzers/test_issues.py

@@ -0,0 +1,167 @@
+"""Tests for issue analyzer."""
+
+import pytest
+from datetime import datetime, timezone, timedelta
+from unittest.mock import Mock
+
+from src.github_analyzer.analyzers.issues import IssueAnalyzer
+from src.github_analyzer.api.models import Issue
+from src.github_analyzer.config.validation import Repository
+
+
+class TestIssueAnalyzerInit:
+    """Tests for IssueAnalyzer initialization."""
+
+    def test_initializes_with_client(self):
+        """Test analyzer initializes with client."""
+        client = Mock()
+        analyzer = IssueAnalyzer(client)
+        assert analyzer._client is client
+
+
+class TestIssueAnalyzerFetchAndAnalyze:
+    """Tests for fetch_and_analyze method."""
+
+    def test_fetches_issues_from_api(self):
+        """Test fetches issues from GitHub API."""
+        client = Mock()
+        client.paginate.return_value = []
+
+        analyzer = IssueAnalyzer(client)
+        repo = Repository(owner="test", name="repo")
+        since = datetime.now(timezone.utc)
+
+        result = analyzer.fetch_and_analyze(repo, since)
+
+        client.paginate.assert_called_once()
+        assert result == []
+
+    def test_filters_out_pull_requests(self):
+        """Test filters out items that are pull requests."""
+        now = datetime.now(timezone.utc)
+        created = now.isoformat()
+
+        client = Mock()
+        client.paginate.return_value = [
+            {"number": 1, "title": "Issue", "state": "open", "created_at": created, "updated_at": created, "user": {"login": "user1"}},
+            {"number": 2, "title": "PR", "state": "open", "created_at": created, "updated_at": created, "pull_request": {}, "user": {"login": "user1"}},
+        ]
+
+        analyzer = IssueAnalyzer(client)
+        repo = Repository(owner="test", name="repo")
+        since = now - timedelta(days=30)
+
+        result = analyzer.fetch_and_analyze(repo, since)
+
+        # Only issue should be included, not PR
+        assert len(result) == 1
+        assert result[0].number == 1
+
+    def test_processes_issues_into_objects(self):
+        """Test processes raw issues into Issue objects."""
+        now = datetime.now(timezone.utc)
+        created = now.isoformat()
+
+        raw_issue = {
+            "number": 1,
+            "title": "Test Issue",
+            "state": "open",
+            "user": {"login": "testuser"},
+            "created_at": created,
+            "updated_at": created,
+            "closed_at": None,
+            "labels": [{"name": "bug"}],
+            "assignees": [{"login": "assignee1"}],
+            "comments": 5,
+            "html_url": "https://github.com/test/repo/issues/1",
+        }
+
+        client = Mock()
+        client.paginate.return_value = [raw_issue]
+
+        analyzer = IssueAnalyzer(client)
+        repo = Repository(owner="test", name="repo")
+        since = now - timedelta(days=30)
+
+        result = analyzer.fetch_and_analyze(repo, since)
+
+        assert len(result) == 1
+        assert isinstance(result[0], Issue)
+        assert result[0].number == 1
+        assert result[0].title == "Test Issue"
+        assert result[0].author_login == "testuser"
+
+
+class TestIssueAnalyzerGetStats:
+    """Tests for get_stats method."""
+
+    def test_returns_empty_stats_for_no_issues(self):
+        """Test returns zeros for empty issue list."""
+        client = Mock()
+        analyzer = IssueAnalyzer(client)
+
+        stats = analyzer.get_stats([])
+
+        assert stats["total"] == 0
+        assert stats["open"] == 0
+        assert stats["closed"] == 0
+        assert stats["bugs"] == 0
+        assert stats["enhancements"] == 0
+        assert stats["avg_time_to_close_hours"] is None
+
+    def test_calculates_correct_stats(self):
+        """Test calculates correct statistics."""
+        client = Mock()
+        analyzer = IssueAnalyzer(client)
+
+        now = datetime.now(timezone.utc)
+        issues = [
+            Issue(
+                repository="test/repo",
+                number=1,
+                title="Open Bug",
+                state="open",
+                author_login="user1",
+                created_at=now - timedelta(days=5),
+                updated_at=now,
+                closed_at=None,
+                labels=["bug"],
+                assignees=["user1"],
+                comments=2,
+            ),
+            Issue(
+                repository="test/repo",
+                number=2,
+                title="Closed Enhancement",
+                state="closed",
+                author_login="user2",
+                created_at=now - timedelta(days=10),
+                updated_at=now - timedelta(days=2),
+                closed_at=now - timedelta(days=2),
+                labels=["enhancement"],
+                assignees=[],
+                comments=5,
+            ),
+            Issue(
+                repository="test/repo",
+                number=3,
+                title="Closed Bug",
+                state="closed",
+                author_login="user3",
+                created_at=now - timedelta(days=3),
+                updated_at=now - timedelta(days=1),
+                closed_at=now - timedelta(days=1),
+                labels=["bug"],
+                assignees=["user3"],
+                comments=1,
+            ),
+        ]
+
+        stats = analyzer.get_stats(issues)
+
+        assert stats["total"] == 3
+        assert stats["open"] == 1
+        assert stats["closed"] == 2
+        assert stats["bugs"] == 2
+        assert stats["enhancements"] == 1
+        assert stats["avg_time_to_close_hours"] is not None