feature: default behavior now is to ignore duplicate paths specified from the command line. Use --keep-duplicates to retain duplicate paths.

testing/python/collect.py

@@ -1213,3 +1213,40 @@ def test_syntax_error_with_non_ascii_chars(testdir):
         '*SyntaxError*',
         '*1 error in*',
     ])
+
+
+def test_skip_duplicates_by_default(testdir):
+    """Test for issue https://github.com/pytest-dev/pytest/issues/1609 (#1609)
+
+    Ignore duplicate directories.
+    """
+    a = testdir.mkdir("a")
+    fh = a.join("test_a.py")
+    fh.write(_pytest._code.Source("""
+        import pytest
+        def test_real():
+            pass
+    """))
+    result = testdir.runpytest(a.strpath, a.strpath)
+    result.stdout.fnmatch_lines([
+        '*collected 1 item*',
+    ])
+
+
+
+def test_keep_duplicates(testdir):
+    """Test for issue https://github.com/pytest-dev/pytest/issues/1609 (#1609)
+
+    Use --keep-duplicates to collect tests from duplicate directories.
+    """
+    a = testdir.mkdir("a")
+    fh = a.join("test_a.py")
+    fh.write(_pytest._code.Source("""
+        import pytest
+        def test_real():
+            pass
+    """))
+    result = testdir.runpytest("--keep-duplicates", a.strpath, a.strpath)
+    result.stdout.fnmatch_lines([
+        '*collected 2 item*',
+    ])

testing/python/metafunc.py

@@ -973,7 +973,7 @@ class TestMetafuncFunctional:
         """))
         sub1.join("test_in_sub1.py").write("def test_1(): pass")
         sub2.join("test_in_sub2.py").write("def test_2(): pass")
-        result = testdir.runpytest("-v", "-s", sub1, sub2, sub1)
+        result = testdir.runpytest("--keep-duplicates", "-v", "-s", sub1, sub2, sub1)
         result.assert_outcomes(passed=3)
 
     def test_generate_same_function_names_issue403(self, testdir):