Add a simple integration test

tests/conftest.py

@@ -1,7 +1,6 @@
-from unittest import mock
-
 import pytest
 
+from lazy_build import cache
 from lazy_build import config
 
 
@@ -15,6 +14,6 @@ def simple_config():
         command=('touch venv'),
         ignore={'*.py[co]'},
         output={'venv'},
-        backend=mock.Mock(),
+        backend=cache.FilesystemBackend(path='cache'),
         after_download=(),
     )

tests/integration_test.py

@@ -0,0 +1,71 @@
+import json
+
+import pytest
+
+from lazy_build import main
+
+
+@pytest.fixture
+def simple_project(tmpdir):
+    tmpdir.join('.lazy-build.json').write(json.dumps({
+        'cache': {
+            'source': 'filesystem',
+            'path': 'cache',
+        },
+    }))
+    tmpdir.join('cache').mkdir()
+    tmpdir.join('input').write('first input\n')
+    tmpdir.join('test.sh').write(
+        'echo ohai\n'
+        'cat input > output1\n'
+        'mkdir -p output2\n'
+        'echo asdf > output2/thing\n'
+    )
+    with tmpdir.as_cwd():
+        yield tmpdir
+
+
+def test_typical_flow(simple_project, capfd):
+    """Test that it correctly caches based on the inputs."""
+    args = (
+        'build',
+        'context=', 'input',
+        'output=', 'output1', 'output2',
+        'command=', 'bash', 'test.sh',
+    )
+
+    def cleanup():
+        simple_project.join('output1').remove()
+        simple_project.join('output2').remove()
+
+    # The first run shouldn't be cached.
+    main.main(args)
+    out, err = capfd.readouterr()
+    assert out == 'ohai\n'
+    assert simple_project.join('output1').read() == 'first input\n'
+    assert simple_project.join('output2', 'thing').read() == 'asdf\n'
+
+    # The second run should be cached.
+    cleanup()
+    main.main(args)
+    out, err = capfd.readouterr()
+    assert out == ''
+    assert simple_project.join('output1').read() == 'first input\n'
+    assert simple_project.join('output2', 'thing').read() == 'asdf\n'
+
+    # If we change the input, it shouldn't be cached anymore.
+    cleanup()
+    simple_project.join('input').write('second input\n')
+    main.main(args)
+    out, err = capfd.readouterr()
+    assert out == 'ohai\n'
+    assert simple_project.join('output1').read() == 'second input\n'
+    assert simple_project.join('output2', 'thing').read() == 'asdf\n'
+
+    # But the next run with the same input should be cached.
+    cleanup()
+    main.main(args)
+    out, err = capfd.readouterr()
+    assert out == ''
+    assert simple_project.join('output1').read() == 'second input\n'
+    assert simple_project.join('output2', 'thing').read() == 'asdf\n'