diff --git a/README.md b/README.md
index 82e79b0..068f860 100644
--- a/README.md
+++ b/README.md
@@ -69,7 +69,11 @@ If you want to forget particular old test results without retesting, run `git te
 
 If you want to permanently forget *all* stored results for a particular test (e.g., if something in your environment has changed), run
 
-    git test forget-results [--test=<name>]
+    git test forget-results --all [--test=<name>]
+
+If you want to permanently forget *all* stored results for *all test*, run
+
+    git test forget-results --all-tests
 
 ### Continue on test failures
 
diff --git a/bin/git-test b/bin/git-test
index d8ddbb2..6490e94 100755
--- a/bin/git-test
+++ b/bin/git-test
@@ -826,7 +826,25 @@ def cmd_results(parser, options):
 
 
 def cmd_forget_results(parser, options):
-    test = Test(options.test)
+    NO_ARGUMENTS_WARNING = """\
+WARNING: Which test results to forget was not specified. Assuming --all for
+backwards compability. This backwards compability might be removed in the
+future, please update to explicit specify what should be removed.
+"""
+
+    if not (options.all or options.all_tests):
+        sys.stderr.write(colored(NO_ARGUMENTS_WARNING, AnsiColor.CYAN))
+        options.all = True
+
+    if options.all_tests:
+        for test in iter_tests():
+            forget_results_for_test(test.name)
+    else:
+        forget_results_for_test(options.test)
+
+
+def forget_results_for_test(name):
+    test = Test(name)
 
     cmd = ['git', 'config', 'test.%s.command' % (test.name,)]
     try:
@@ -838,6 +856,9 @@ def cmd_forget_results(parser, options):
         test.initialize_status(
             'Test results reinitialized by \'git test forget-results\''
             )
+        sys.stdout.write(colored('All test results for test ', AnsiColor.GREEN))
+        sys.stdout.write(colored(test.name, AnsiColor.CYAN))
+        sys.stdout.write(colored(' were forgotten.\n', AnsiColor.GREEN))
 
 
 test_re = re.compile(r'^test\.(?P<name>.*)\.command$')
@@ -1058,6 +1079,15 @@ def main(args):
         action='store', default='default',
         help='name of test whose results should be forgotten (default is \'default\')',
         )
+    subparser.add_argument(
+        '--all', action='store_true',
+        help='forget all existing test results for the current test',
+        )
+    subparser.add_argument(
+        '--all-tests',
+        action='store_true',
+        help='forget all existing test results for all tests',
+        )
     add_verbosity_options(subparser)
 
     subparser = subparsers.add_parser(
diff --git a/test/forget-results.t b/test/forget-results.t
new file mode 100755
index 0000000..dd7d3c0
--- /dev/null
+++ b/test/forget-results.t
@@ -0,0 +1,164 @@
+#! /bin/sh
+
+test_description="Test forgetting test results"
+
+. ./sharness.sh
+
+test_expect_success 'Set up test repository' '
+	git init . &&
+	git config user.name "Test User" &&
+	git config user.email "user@example.com" &&
+	for i in $(seq 0 3)
+	do
+		echo $i >number &&
+		git add number &&
+		git commit -m "Number $i"
+	done &&
+	true
+'
+
+test_expect_success 'Add tests' '
+	git-test add true &&
+	git-test add -t t1 true &&
+	git-test add -t t2 true &&
+	git-test add -t t3 true &&
+	true
+'
+
+test_expect_success 'Add some simulated test results' '
+	git notes --ref=tests/default add -m "good" HEAD~0^{tree} &&
+	git notes --ref=tests/default add -m "good" HEAD~1^{tree} &&
+	git notes --ref=tests/default add -m "good" HEAD~2^{tree} &&
+	git notes --ref=tests/default add -m "good" HEAD~3^{tree} &&
+	true &&
+	git notes --ref=tests/t1 add -m "good" HEAD~0^{tree} &&
+	git notes --ref=tests/t1 add -m "good" HEAD~1^{tree} &&
+	git notes --ref=tests/t1 add -m "good" HEAD~2^{tree} &&
+	git notes --ref=tests/t1 add -m "bad" HEAD~3^{tree} &&
+	true &&
+	git notes --ref=tests/t2 add -m "good" HEAD~1^{tree} &&
+	git notes --ref=tests/t2 add -m "bad" HEAD~2^{tree} &&
+	true
+'
+
+test_expect_success 'Verify number of notes' '
+	echo 4 > expected &&
+	git notes --ref=tests/default list | wc -l >actual &&
+	test_cmp expected actual &&
+	true &&
+	echo 4 > expected &&
+	git notes --ref=tests/t1 list | wc -l >actual &&
+	test_cmp expected actual &&
+	true &&
+	echo 2 > expected &&
+	git notes --ref=tests/t2 list | wc -l >actual &&
+	test_cmp expected actual &&
+	true &&
+	echo 0 > expected &&
+	git notes --ref=tests/t3 list | wc -l >actual &&
+	test_cmp expected actual &&
+	true
+'
+
+test_expect_success 'Forgetting default and not affecting other tests' '
+	echo "All test results for test default were forgotten." >expected &&
+	git-test forget-results --all >actual &&
+	test_must_fail grep -q WARNING actual
+	test_cmp expected actual &&
+	echo 0 > expected &&
+	git notes --ref=tests/default list | wc -l >actual &&
+	test_cmp expected actual &&
+	true &&
+	echo 4 > expected &&
+	git notes --ref=tests/t1 list | wc -l >actual &&
+	test_cmp expected actual &&
+	true &&
+	echo 2 > expected &&
+	git notes --ref=tests/t2 list | wc -l >actual &&
+	test_cmp expected actual &&
+	true &&
+	echo 0 > expected &&
+	git notes --ref=tests/t3 list | wc -l >actual &&
+	test_cmp expected actual &&
+	true
+'
+
+
+test_expect_success 'Add default test results again' '
+	git notes --ref=tests/default add -m "good" HEAD~0^{tree} &&
+	git notes --ref=tests/default add -m "good" HEAD~1^{tree} &&
+	git notes --ref=tests/default add -m "good" HEAD~2^{tree} &&
+	git notes --ref=tests/default add -m "good" HEAD~3^{tree} &&
+	true
+'
+
+
+test_expect_success 'Forgetting t1 and not affecting other tests' '
+	echo "All test results for test t1 were forgotten." >expected &&
+	git-test forget-results --all --test t1 >actual &&
+	test_must_fail grep -q WARNING actual
+	test_cmp expected actual &&
+	echo 4 > expected &&
+	git notes --ref=tests/default list | wc -l >actual &&
+	test_cmp expected actual &&
+	true &&
+	echo 0 > expected &&
+	git notes --ref=tests/t1 list | wc -l >actual &&
+	test_cmp expected actual &&
+	true &&
+	echo 2 > expected &&
+	git notes --ref=tests/t2 list | wc -l >actual &&
+	test_cmp expected actual &&
+	true &&
+	echo 0 > expected &&
+	git notes --ref=tests/t3 list | wc -l >actual &&
+	test_cmp expected actual &&
+	true
+'
+
+test_expect_success 'Forgetting all test results' '
+	echo "All test results for test default were forgotten." >expected &&
+	echo "All test results for test t1 were forgotten." >>expected &&
+	echo "All test results for test t2 were forgotten." >>expected &&
+	echo "All test results for test t3 were forgotten." >>expected &&
+	git-test forget-results --all-tests >actual &&
+	test_must_fail grep -q WARNING actual
+	test_cmp expected actual &&
+	echo 0 > expected &&
+	git notes --ref=tests/default list | wc -l >actual &&
+	test_cmp expected actual &&
+	true &&
+	echo 0 > expected &&
+	git notes --ref=tests/t1 list | wc -l >actual &&
+	test_cmp expected actual &&
+	true &&
+	echo 0 > expected &&
+	git notes --ref=tests/t2 list | wc -l >actual &&
+	test_cmp expected actual &&
+	true &&
+	echo 0 > expected &&
+	git notes --ref=tests/t3 list | wc -l >actual &&
+	test_cmp expected actual &&
+	true
+'
+
+
+# sed command: On line 1 remove from the first space and the rest, and delete
+# lines 2 and till the last line, e.g. only keep first word on first line.
+test_expect_success 'Missing --all or --all-tests argument produces warning' '
+	echo "WARNING:" >expected
+	git-test forget-results 2>actual &&
+	sed -i "1s/ .*//; 2,\$d" actual &&
+	test_cmp expected actual
+'
+
+
+test_expect_success 'Should not give output on non-existent test' '
+	rm -f expected &&
+	touch expected &&
+	git-test forget-results --all -t this-test-does-not-exist >actual &&
+	test_cmp expected actual &&
+	true
+'
+
+test_done