test: a true unit test for render_report

1 files changed, 50 insertions, 0 deletions

diff --git a/tests/test_report.py b/tests/test_report.py
new file mode 100644
index 00000000..1a9dd179
--- /dev/null
+++ b/tests/test_report.py
@@ -0,0 +1,50 @@
+# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
+# For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
+
+"""Tests for helpers in report.py"""
+
+import pytest
+
+from coverage.exceptions import CoverageException
+from coverage.report import render_report
+from tests.coveragetest import CoverageTest
+
+
+class FakeReporter:
+    """A fake implementation of a one-file reporter."""
+
+    def __init__(self, output="", error=False):
+        self.output = output
+        self.error = error
+        self.morfs = None
+
+    def report(self, morfs, outfile):
+        """Fake."""
+        self.morfs = morfs
+        outfile.write(self.output)
+        if self.error:
+            raise CoverageException("You asked for it!")
+
+
+class RenderReportTest(CoverageTest):
+    """Tests of render_report."""
+
+    def test_stdout(self):
+        fake = FakeReporter(output="Hello!\n")
+        render_report("-", fake, [pytest, "coverage"])
+        assert fake.morfs == [pytest, "coverage"]
+        assert self.stdout() == "Hello!\n"
+
+    def test_file(self):
+        fake = FakeReporter(output="Gréètings!\n")
+        render_report("output.txt", fake, [])
+        assert self.stdout() == ""
+        with open("output.txt", "rb") as f:
+            assert f.read() == b"Gr\xc3\xa9\xc3\xa8tings!\n"
+
+    def test_exception(self):
+        fake = FakeReporter(error=True)
+        with pytest.raises(CoverageException, match="You asked for it!"):
+            render_report("output.txt", fake, [])
+        assert self.stdout() == ""
+        self.assert_doesnt_exist("output.txt")