test: add tests of the failure asserts from check_coverage

This brings the coverage of tests/coveragetest.py to 100%.

2 files changed, 54 insertions, 3 deletions

diff --git a/tests/coveragetest.py b/tests/coveragetest.py
index 9b7fe167..3363fa89 100644
--- a/tests/coveragetest.py
+++ b/tests/coveragetest.py
@@ -55,7 +55,7 @@ class CoverageTest(
 
     # Temp dirs go to $TMPDIR/coverage_test/*
     temp_dir_prefix = "coverage_test/"
-    if os.getenv('COVERAGE_ENV_ID'):
+    if os.getenv('COVERAGE_ENV_ID'):                        # pragma: debugging
         temp_dir_prefix += "{}/".format(os.getenv('COVERAGE_ENV_ID'))
 
     # Keep the temp directories if the env says to.
@@ -115,8 +115,8 @@ class CoverageTest(
         s1 = arcs_to_arcz_repr(a1)
         s2 = arcs_to_arcz_repr(a2)
         if s1 != s2:
-            lines1 = s1.splitlines(keepends=True)
-            lines2 = s2.splitlines(keepends=True)
+            lines1 = s1.splitlines(True)
+            lines2 = s2.splitlines(True)
             diff = "".join(difflib.ndiff(lines1, lines2))
             return "\n" + arc_type + " arcs differ: minus is expected, plus is actual\n" + diff
         else:
diff --git a/tests/test_testing.py b/tests/test_testing.py
index 67ec8dff..f5d9f942 100644
--- a/tests/test_testing.py
+++ b/tests/test_testing.py
@@ -245,6 +245,57 @@ class CheckUniqueFilenamesTest(CoverageTest):
             stub.method("file1")
 
 
+class CheckCoverageTest(CoverageTest):
+    """Tests of the failure assertions in check_coverage."""
+
+    CODE = """\
+        a, b = 1, 1
+        def oops(x):
+            if x % 2:
+                raise Exception("odd")
+        try:
+            a = 6
+            oops(1)
+            a = 8
+        except:
+            b = 10
+        assert a == 6 and b == 10
+        """
+    ARCZ = ".1 12 -23 34 3-2 4-2 25 56 67 78 8B 9A AB B."
+    ARCZ_MISSING = "3-2 78 8B"
+    ARCZ_UNPREDICTED = "79"
+
+    def test_check_coverage_possible(self):
+        msg = r"(?s)Possible arcs differ: .*- \(6, 3\).*\+ \(6, 7\)"
+        with pytest.raises(AssertionError, match=msg):
+            self.check_coverage(
+                self.CODE,
+                arcz=self.ARCZ.replace("7", "3"),
+                arcz_missing=self.ARCZ_MISSING,
+                arcz_unpredicted=self.ARCZ_UNPREDICTED,
+            )
+
+    def test_check_coverage_missing(self):
+        msg = r"(?s)Missing arcs differ: .*- \(3, 8\).*\+ \(7, 8\)"
+        with pytest.raises(AssertionError, match=msg):
+            self.check_coverage(
+                self.CODE,
+                arcz=self.ARCZ,
+                arcz_missing=self.ARCZ_MISSING.replace("7", "3"),
+                arcz_unpredicted=self.ARCZ_UNPREDICTED,
+            )
+
+    def test_check_coverage_unpredicted(self):
+        msg = r"(?s)Unpredicted arcs differ: .*- \(3, 9\).*\+ \(7, 9\)"
+        with pytest.raises(AssertionError, match=msg):
+            self.check_coverage(
+                self.CODE,
+                arcz=self.ARCZ,
+                arcz_missing=self.ARCZ_MISSING,
+                arcz_unpredicted=self.ARCZ_UNPREDICTED.replace("7", "3")
+            )
+
+
 @pytest.mark.parametrize("text, pat, result", [
     ("line1\nline2\nline3\n", "line", "line1\nline2\nline3\n"),
     ("line1\nline2\nline3\n", "[13]", "line1\nline3\n"),