pytest conftest.py patterns for shared fixtures

<p>Test fixtures are duplicated across multiple test files. Each file has its own database setup, mock clients, and test data factories. Need a way to share fixtures across an entire test suite without importing from test files.</p>

<p>Organize conftest.py files hierarchically — pytest discovers them automatically:</p> <div class="highlight"><pre><span></span><code>tests/ conftest.py # Session-wide fixtures (DB engine, app client) factories.py # Test data factories unit/ conftest.py # Unit test specific fixtures (no DB) test_tags.py integration/ conftest.py # Integration fixtures (with DB) test_traces.py </code></pre></div> <div class="highlight"><pre><span></span><code><span class="c1"># tests/factories.py — factory functions for test data</span> <span class="kn">import</span><span class="w"> </span><span class="nn">uuid</span> <span class="kn">from</span><span class="w"> </span><span class="nn">datetime</span><span class="w"> </span><span class="kn">import</span> <span class="n">datetime</span> <span class="k">def</span><span class="w"> </span><span class="nf">make_trace</span><span class="p">(</span><span class="o">**</span><span class="n">overrides</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="nb">dict</span><span class="p">:</span> <span class="k">return</span> <span class="p">{</span> <span class="s1">'id'</span><span class="p">:</span> <span class="nb">str</span><span class="p">(</span><span class="n">uuid</span><span class="o">.</span><span class="n">uuid4</span><span class="p">()),</span> <span class="s1">'title'</span><span class="p">:</span> <span class="s1">'Test trace title'</span><span class="p">,</span> <span class="s1">'context_text'</span><span class="p">:</span> <span class="s1">'Test context text'</span><span class="p">,</span> <span class="s1">'solution_text'</span><span class="p">:</span> <span class="s1">'Test solution text'</span><span class="p">,</span> <span class="s1">'status'</span><span class="p">:</span> <span class="s1">'pending'</span><span class="p">,</span> <span class="s1">'trust_score'</span><span class="p">:</span> <span class="mf">0.0</span><span class="p">,</span> <span class="s1">'is_seed'</span><span class="p">:</span> <span class="kc">False</span><span class="p">,</span> <span class="s1">'created_at'</span><span class="p">:</span> <span class="n">datetime</span><span class="o">.</span><span class="n">utcnow</span><span class="p">(),</span> <span class="o">**</span><span class="n">overrides</span> <span class="p">}</span> <span class="c1"># tests/conftest.py — top-level, available everywhere</span> <span class="kn">import</span><span class="w"> </span><span class="nn">pytest</span> <span class="kn">import</span><span class="w"> </span><span class="nn">pytest_asyncio</span> <span class="kn">from</span><span class="w"> </span><span class="nn">tests.factories</span><span class="w"> </span><span class="kn">import</span> <span class="n">make_trace</span> <span class="nd">@pytest</span><span class="o">.</span><span class="n">fixture</span><span class="p">(</span><span class="n">scope</span><span class="o">=</span><span class="s1">'session'</span><span class="p">)</span> <span class="k">def</span><span class="w"> </span><span class="nf">event_loop_policy</span><span class="p">():</span> <span class="c1"># Ensure same event loop policy across session</span> <span class="kn">import</span><span class="w"> </span><span class="nn">asyncio</span> <span class="k">return</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">DefaultEventLoopPolicy</span><span class="p">()</span> <span class="nd">@pytest_asyncio</span><span class="o">.</span><span class="n">fixture</span><span class="p">(</span><span class="n">scope</span><span class="o">=</span><span class="s1">'session'</span><span class="p">)</span> <span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">app</span><span class="p">():</span> <span class="kn">from</span><span class="w"> </span><span class="nn">app.main</span><span class="w"> </span><span class="kn">import</span> <span class="n">app</span> <span class="k">as</span> <span class="n">fastapi_app</span> <span class="k">return</span> <span class="n">fastapi_app</span> <span class="c1"># tests/integration/conftest.py — integration-specific</span> <span class="nd">@pytest_asyncio</span><span class="o">.</span><span class="n">fixture</span> <span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">trace_in_db</span><span class="p">(</span><span class="n">session</span><span class="p">,</span> <span class="n">seed_user</span><span class="p">):</span> <span class="n">data</span> <span class="o">=</span> <span class="n">make_trace</span><span class="p">(</span><span class="n">contributor_id</span><span class="o">=</span><span class="nb">str</span><span class="p">(</span><span class="n">seed_user</span><span class="o">.</span><span class="n">id</span><span class="p">))</span> <span class="n">trace</span> <span class="o">=</span> <span class="n">Trace</span><span class="p">(</span><span class="o">**</span><span class="p">{</span><span class="n">k</span><span class="p">:</span> <span class="n">v</span> <span class="k">for</span> <span class="n">k</span><span class="p">,</span> <span class="n">v</span> <span class="ow">in</span> <span class="n">data</span><span class="o">.</span><span class="n">items</span><span class="p">()</span> <span class="k">if</span> <span class="n">k</span> <span class="o">!=</span> <span class="s1">'id'</span><span class="p">})</span> <span class="n">session</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">trace</span><span class="p">)</span> <span class="k">await</span> <span class="n">session</span><span class="o">.</span><span class="n">flush</span><span class="p">()</span> <span class="k">return</span> <span class="n">trace</span> <span class="nd">@pytest_asyncio</span><span class="o">.</span><span class="n">fixture</span> <span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">validated_trace</span><span class="p">(</span><span class="n">session</span><span class="p">,</span> <span class="n">seed_user</span><span class="p">):</span> <span class="n">trace</span> <span class="o">=</span> <span class="n">Trace</span><span class="p">(</span><span class="o">**</span><span class="n">make_trace</span><span class="p">(</span> <span class="n">contributor_id</span><span class="o">=</span><span class="nb">str</span><span class="p">(</span><span class="n">seed_user</span><span class="o">.</span><span class="n">id</span><span class="p">),</span> <span class="n">status</span><span class="o">=</span><span class="s1">'validated'</span><span class="p">,</span> <span class="n">trust_score</span><span class="o">=</span><span class="mf">0.8</span><span class="p">,</span> <span class="n">confirmation_count</span><span class="o">=</span><span class="mi">3</span><span class="p">,</span> <span class="p">))</span> <span class="n">session</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">trace</span><span class="p">)</span> <span class="k">await</span> <span class="n">session</span><span class="o">.</span><span class="n">flush</span><span class="p">()</span> <span class="k">return</span> <span class="n">trace</span> <span class="c1"># tests/unit/conftest.py — no DB needed</span> <span class="nd">@pytest</span><span class="o">.</span><span class="n">fixture</span> <span class="k">def</span><span class="w"> </span><span class="nf">mock_redis</span><span class="p">(</span><span class="n">mocker</span><span class="p">):</span> <span class="k">return</span> <span class="n">mocker</span><span class="o">.</span><span class="n">AsyncMock</span><span class="p">()</span> </code></pre></div> <p>Fixtures in <code>tests/conftest.py</code> are available to all tests. Fixtures in <code>tests/integration/conftest.py</code> only to <code>tests/integration/</code> tests. Use <code>pytest-factoryboy</code> or hand-rolled factories for test data. Never import from test files — put shared code in <code>conftest.py</code> or utility modules.</p>