Fix --last-failed reported items in terminal

_pytest/cacheprovider.py

@@ -106,14 +106,18 @@ def __init__(self, config):
         active_keys = 'lf', 'failedfirst'
         self.active = any(config.getvalue(key) for key in active_keys)
         self.lastfailed = config.cache.get("cache/lastfailed", {})
+        self._previously_failed_count = None
 
-    def pytest_report_header(self):
+    def pytest_report_collectionfinish(self):
         if self.active:
-            if not self.lastfailed:
+            if not self._previously_failed_count:
                 mode = "run all (no recorded failures)"
             else:
-                mode = "rerun previous failures%s" % (
-                    " first" if self.config.getvalue("failedfirst") else "")
+                noun = 'failure' if self._previously_failed_count == 1 else 'failures'
+                suffix = " first" if self.config.getvalue("failedfirst") else ""
+                mode = "rerun previous {count} {noun}{suffix}".format(
+                    count=self._previously_failed_count, suffix=suffix, noun=noun
+                )
             return "run-last-failure: %s" % mode
 
     def pytest_runtest_logreport(self, report):
@@ -142,6 +146,7 @@ def pytest_collection_modifyitems(self, session, config, items):
                     previously_failed.append(item)
                 else:
                     previously_passed.append(item)
+            self._previously_failed_count = len(previously_failed)
             if not previously_failed:
                 # running a subset of all tests with recorded failures outside
                 # of the set of tests currently executing

_pytest/hookspec.py

@@ -351,7 +351,10 @@ def pytest_report_header(config, startdir):
 
 
 def pytest_report_collectionfinish(config, startdir, items):
-    """ return a string or list of strings to be displayed after collection has finished successfully.
+    """
+    .. versionadded:: 3.2
+
+    return a string or list of strings to be displayed after collection has finished successfully.
 
     This strings will be displayed after the standard "collected X items" message.
 

testing/test_cache.py

@@ -340,6 +340,73 @@ def test_fail(val):
         result = testdir.runpytest()
         result.stdout.fnmatch_lines('*1 failed in*')
 
+    def test_terminal_report_lastfailed(self, testdir):
+        test_a = testdir.makepyfile(test_a="""
+            def test_a1():
+                pass
+            def test_a2():
+                pass
+        """)
+        test_b = testdir.makepyfile(test_b="""
+            def test_b1():
+                assert 0
+            def test_b2():
+                assert 0
+        """)
+        result = testdir.runpytest()
+        result.stdout.fnmatch_lines([
+            'collected 4 items',
+            '*2 failed, 2 passed in*',
+        ])
+
+        result = testdir.runpytest('--lf')
+        result.stdout.fnmatch_lines([
+            'collected 4 items',
+            'run-last-failure: rerun previous 2 failures',
+            '*2 failed, 2 deselected in*',
+        ])
+
+        result = testdir.runpytest(test_a, '--lf')
+        result.stdout.fnmatch_lines([
+            'collected 2 items',
+            'run-last-failure: run all (no recorded failures)',
+            '*2 passed in*',
+        ])
+
+        result = testdir.runpytest(test_b, '--lf')
+        result.stdout.fnmatch_lines([
+            'collected 2 items',
+            'run-last-failure: rerun previous 2 failures',
+            '*2 failed in*',
+        ])
+
+        result = testdir.runpytest('test_b.py::test_b1', '--lf')
+        result.stdout.fnmatch_lines([
+            'collected 1 item',
+            'run-last-failure: rerun previous 1 failure',
+            '*1 failed in*',
+        ])
+
+    def test_terminal_report_failedfirst(self, testdir):
+        testdir.makepyfile(test_a="""
+            def test_a1():
+                assert 0
+            def test_a2():
+                pass
+        """)
+        result = testdir.runpytest()
+        result.stdout.fnmatch_lines([
+            'collected 2 items',
+            '*1 failed, 1 passed in*',
+        ])
+
+        result = testdir.runpytest('--ff')
+        result.stdout.fnmatch_lines([
+            'collected 2 items',
+            'run-last-failure: rerun previous 1 failure first',
+            '*1 failed, 1 passed in*',
+        ])
+
     def test_lastfailed_collectfailure(self, testdir, monkeypatch):
 
         testdir.makepyfile(test_maybe="""