fix: only accept known values for --format

3 files changed, 13 insertions, 1 deletions

diff --git a/coverage/summary.py b/coverage/summary.py
index fe73c678..24aa30f2 100644
--- a/coverage/summary.py
+++ b/coverage/summary.py
@@ -20,11 +20,12 @@ class SummaryReporter:
         self.branches = coverage.get_data().has_arcs()
         self.outfile = None
         self.output_format = self.config.format or "text"
+        if self.output_format not in {"text", "markdown", "total"}:
+            raise ConfigError(f"Unknown report format choice: {self.output_format!r}")
         self.fr_analysis = []
         self.skipped_count = 0
         self.empty_count = 0
         self.total = Numbers(precision=self.config.precision)
-        self.fmt_err = "%s   %s: %s"
 
     def write(self, line):
         """Write a line to the output, adding a newline."""
diff --git a/tests/test_cmdline.py b/tests/test_cmdline.py
index 378c901d..96e7ffb9 100644
--- a/tests/test_cmdline.py
+++ b/tests/test_cmdline.py
@@ -585,6 +585,11 @@ class CmdLineTest(BaseCmdLineTest):
             cov.load()
             cov.report(show_missing=None)
             """)
+        self.cmd_executes("report --format=markdown", """\
+            cov = Coverage()
+            cov.load()
+            cov.report(output_format="markdown")
+            """)
 
     def test_run(self):
         # coverage run [-p] [-L] [--timid] MODULE.py [ARG1 ARG2 ...]
diff --git a/tests/test_summary.py b/tests/test_summary.py
index 82508de8..f0f16aa2 100644
--- a/tests/test_summary.py
+++ b/tests/test_summary.py
@@ -1001,3 +1001,9 @@ class SummaryReporterConfigurationTest(CoverageTest):
         msg = "Invalid sorting option: 'Xyzzy'"
         with pytest.raises(ConfigError, match=msg):
             self.get_summary_text(('report:sort', 'Xyzzy'))
+
+    def test_report_with_invalid_format(self):
+        # Ask for an invalid format.
+        msg = "Unknown report format choice: 'xyzzy'"
+        with pytest.raises(ConfigError, match=msg):
+            self.get_summary_text(('report:format', 'xyzzy'))