Add --snapshot-strict switch

.travis.yml

@@ -9,9 +9,9 @@ cache: pip
 install:
 - pip install -e .[test]
 script:
-- py.test --cov=snapshottest tests examples/pytest
+- py.test --cov=snapshottest --snapshot-strict tests examples/pytest
 # Run Pytest Example
-- py.test examples/pytest
+- py.test --snapshot-strict examples/pytest
 # Run Unittest Example
 - python examples/unittest/test_demo.py
 # Run nose

examples/pytest/test_demo.py

@@ -1,4 +1,6 @@
 # -*- coding: utf-8 -*-
+import pytest
+
 from snapshottest.file import FileSnapshot
 
 
@@ -58,3 +60,8 @@ def test_multiple_files(snapshot, tmpdir):
     temp_file1 = tmpdir.join('example2.txt')
     temp_file1.write('Hello, world 2!')
     snapshot.assert_match(FileSnapshot(str(temp_file1)))
+
+
+def test_unused_snapshot_should_be_reject_in_strict_mode(snapshot):
+    with pytest.raises(AssertionError, match="Saving snapshots not allowed in strict mode."):
+        snapshot.assert_match(False)

setup.cfg

@@ -6,5 +6,5 @@ exclude = snapshots .tox
 max-line-length = 120
 
 [tool:pytest]
-addopts = --cov snapshottest
+addopts = --cov snapshottest --snapshot-strict
 testpaths = tests

snapshottest/module.py

@@ -4,6 +4,7 @@
 import imp
 from collections import defaultdict
 import logging
+from typing import Set, Iterable
 
 from .snapshot import Snapshot
 from .formatter import Formatter
@@ -48,7 +49,7 @@ def delete_unvisited(self):
             del self.snapshots[unvisited]
 
     @property
-    def unvisited_snapshots(self):
+    def unvisited_snapshots(self) -> Set[str]:
         return set(self.snapshots.keys()) - self.visited_snapshots
 
     @classmethod
@@ -63,7 +64,7 @@ def total_unvisited_snapshots(cls):
         return unvisited_snapshots, unvisited_modules
 
     @classmethod
-    def get_modules(cls):
+    def get_modules(cls) -> Iterable["SnapshotModule"]:
         return SnapshotModule._snapshot_modules.values()
 
     @classmethod
@@ -185,13 +186,22 @@ def get_module_for_testpath(cls, test_filepath):
 
         return cls._snapshot_modules[test_filepath]
 
+    @classmethod
+    def all_unvisited_snapshots(cls) -> Set[str]:
+        unvisited: Set[str] = set()
+        for module in cls.get_modules():
+            unvisited |= {f"{module.filepath}::{snapshot}" for snapshot in module.unvisited_snapshots}
+
+        return unvisited
+
 
 class SnapshotTest(object):
     _current_tester = None
 
-    def __init__(self):
+    def __init__(self, strict=False):
         self.curr_snapshot = ''
         self.snapshot_counter = 1
+        self.strict = strict
 
     @property
     def module(self):
@@ -220,6 +230,7 @@ def fail(self):
         self.module.mark_failed(self.test_name)
 
     def store(self, data):
+        assert not self.strict, "Saving snapshots not allowed in strict mode."
         formatter = Formatter.get_formatter(data)
         data = formatter.store(self, data)
         self.module[self.test_name] = data

snapshottest/pytest.py

@@ -21,13 +21,19 @@ def pytest_addoption(parser):
         default=False,
         help='Dump diagnostic and progress information.'
     )
+    group.addoption(
+        '--snapshot-strict',
+        action='store_true',
+        default=False,
+        help='Fails test if new snapshot is created or some snapshot is unused.'
+    )
 
 
 class PyTestSnapshotTest(SnapshotTest):
 
-    def __init__(self, request=None):
+    def __init__(self, request=None, strict=False):
         self.request = request
-        super(PyTestSnapshotTest, self).__init__()
+        super(PyTestSnapshotTest, self).__init__(strict=strict)
 
     @property
     def module(self):
@@ -50,6 +56,7 @@ def test_name(self):
 class SnapshotSession(object):
     def __init__(self, config):
         self.verbose = config.getoption("snapshot_verbose")
+        self.strict = config.option.snapshot_strict
         self.config = config
 
     def display(self, tr):
@@ -58,7 +65,7 @@ def display(self, tr):
 
         tr.write_sep("=", "SnapshotTest summary")
 
-        for line in reporting_lines('pytest'):
+        for line in reporting_lines('pytest', strict=self.strict):
             tr.write_line(line)
 
 
@@ -69,7 +76,8 @@ def pytest_assertrepr_compare(op, left, right):
 
 @pytest.fixture
 def snapshot(request):
-    with PyTestSnapshotTest(request) as snapshot_test:
+    strict = request.config.option.snapshot_strict
+    with PyTestSnapshotTest(request, strict=strict) as snapshot_test:
         yield snapshot_test
 
 
@@ -82,6 +90,20 @@ def pytest_terminal_summary(terminalreporter):
     terminalreporter.config._snapshotsession.display(terminalreporter)
 
 
+@pytest.hookimpl(trylast=True)
+def pytest_sessionfinish(session, exitstatus):
+    from _pytest.main import EXIT_NOTESTSCOLLECTED, EXIT_OK, EXIT_TESTSFAILED
+
+    unvisited_snapshots = SnapshotModule.all_unvisited_snapshots()
+    if not session.config.option.snapshot_strict or not unvisited_snapshots:
+        return
+
+    if exitstatus not in (EXIT_NOTESTSCOLLECTED, EXIT_OK, EXIT_TESTSFAILED):
+        return
+
+    session.exitstatus = EXIT_TESTSFAILED
+
+
 @pytest.mark.trylast  # force the other plugins to initialise, fixes issue with capture not being properly initialised
 def pytest_configure(config):
     config._snapshotsession = SnapshotSession(config)

snapshottest/reporting.py

@@ -4,7 +4,7 @@
 from .module import SnapshotModule
 
 
-def reporting_lines(testing_cli):
+def reporting_lines(testing_cli, strict=False):
     successful_snapshots = SnapshotModule.stats_successful_snapshots()
     bold = ['bold']
     if successful_snapshots:
@@ -26,12 +26,20 @@ def reporting_lines(testing_cli):
             colored('{} snapshots failed', 'red', attrs=bold) + ' in {} test suites. '
             + inspect_str
         ).format(*failed_snapshots)
-    unvisited_snapshots = SnapshotModule.stats_unvisited_snapshots()
-    if unvisited_snapshots[0]:
-        yield (
-            colored('{} snapshots deprecated', 'yellow', attrs=bold) + ' in {} test suites. '
-            + inspect_str
-        ).format(*unvisited_snapshots)
+    unvisited_snapshots = SnapshotModule.all_unvisited_snapshots()
+    if unvisited_snapshots:
+        if strict:
+            error_msg = colored(f'ERROR: {len(unvisited_snapshots)} snapshots unused.', 'red', attrs=bold)
+            comment = colored("In strict mode all snapshots must be used.",attrs=['dark'])
+            yield f"{error_msg} {comment}"
+            yield colored("Unused snapshots:", "red", attrs=bold)
+            yield from unvisited_snapshots
+
+        else:
+            yield (
+                colored('{} snapshots deprecated', 'yellow', attrs=bold) + ' in {} test suites. '
+                + inspect_str
+            ).format(*unvisited_snapshots)
 
 
 def diff_report(left, right):

tests/test_module.py

@@ -3,7 +3,7 @@
 import pytest
 
 from snapshottest import Snapshot
-from snapshottest.module import SnapshotModule
+from snapshottest.module import SnapshotModule, SnapshotTest
 
 
 class TestSnapshotModuleLoading(object):
@@ -27,3 +27,29 @@ def test_load_corrupted_snapshot(self, tmpdir):
         module = SnapshotModule("tests.snapshots.snap_error", str(filepath))
         with pytest.raises(SyntaxError):
             module.load_snapshots()
+
+
+
+class MockSnapshotTest(SnapshotTest):
+    def __init__(self, *, strict=False, module: SnapshotModule, test_name: str) -> None:
+        super().__init__(strict=strict)
+        self._module = module
+        self._test_name = test_name
+
+    @property
+    def module(self) -> SnapshotModule:
+        return self._module
+
+    @property
+    def test_name(self) -> str:
+        return self._test_name
+
+
+class TestStrictSnapshotModule:
+    def test_should_fail_if_new_snapshots_appear(self, tmpdir):
+        file_with_snapshots = tmpdir.join("snap_new.py")
+        module = SnapshotModule(module="tests.snapshots.snap_new", filepath=str(file_with_snapshots))
+        test = MockSnapshotTest(strict=True, module=module, test_name="Some test")
+
+        with pytest.raises(AssertionError, match="Saving snapshots not allowed in strict mode."):
+            test.assert_match(False)

tests/test_pytest_unused_snapshot.py

@@ -0,0 +1,14 @@
+import subprocess
+
+
+def test_suite_should_fail_for_unused_snapshots(snapshot):
+    completed_process = subprocess.run(
+        ["pytest", "--snapshot-strict", "-v", "tests/unused_snapshot/command.py"],
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+        encoding="utf-8"
+    )
+
+    assert completed_process.returncode == 1
+    assert "test_should_not_use_any_snapshot PASSED" in completed_process.stdout
+    assert "ERROR: 1 snapshots unused" in completed_process.stdout

tests/unused_snapshot/command.py

@@ -0,0 +1,5 @@
+import pytest
+
+
+def test_should_not_use_any_snapshot(snapshot):
+    snapshot.assert_match(True)

tests/unused_snapshot/snapshots/snap_command.py

@@ -0,0 +1,12 @@
+# -*- coding: utf-8 -*-
+# snapshottest: v1 - https://goo.gl/zC4yUc
+from __future__ import unicode_literals
+
+from snapshottest import GenericRepr, Snapshot
+from snapshottest.file import FileSnapshot
+
+
+snapshots = Snapshot()
+
+snapshots['not used'] = {}
+snapshots['test_should_not_use_any_snapshot 1'] = True