diff --git a/t/README b/t/README
index 6404f33e19..9747971d58 100644
--- a/t/README
+++ b/t/README
@@ -334,6 +334,15 @@ that cannot be easily covered by a few specific test cases. These
 could be enabled by running the test suite with correct GIT_TEST_
 environment set.
 
+GIT_TEST_FAIL_PREREQS<non-empty?> fails all prerequisites. This is
+useful for discovering issues with the tests where say a later test
+implicitly depends on an optional earlier test.
+
+There's a "FAIL_PREREQS" prerequisite that can be used to test for
+whether this mode is active, and e.g. skip some tests that are hard to
+refactor to deal with it. The "SYMLINKS" prerequisite is currently
+excluded as so much relies on it, but this might change in the future.
+
 GIT_TEST_GETTEXT_POISON=<non-empty?> turns all strings marked for
 translation into gibberish if non-empty (think "test -n"). Used for
 spotting those tests that need to be marked with a C_LOCALE_OUTPUT
diff --git a/t/t0000-basic.sh b/t/t0000-basic.sh
index c03054c538..31de7e90f3 100755
--- a/t/t0000-basic.sh
+++ b/t/t0000-basic.sh
@@ -726,7 +726,7 @@ donthaveit=yes
 test_expect_success DONTHAVEIT 'unmet prerequisite causes test to be skipped' '
 	donthaveit=no
 '
-if test $haveit$donthaveit != yesyes
+if test -z "$GIT_TEST_FAIL_PREREQS" -a $haveit$donthaveit != yesyes
 then
 	say "bug in test framework: prerequisite tags do not work reliably"
 	exit 1
@@ -747,7 +747,7 @@ donthaveiteither=yes
 test_expect_success DONTHAVEIT,HAVEIT 'unmet prerequisites causes test to be skipped' '
 	donthaveiteither=no
 '
-if test $haveit$donthaveit$donthaveiteither != yesyesyes
+if test -z "$GIT_TEST_FAIL_PREREQS" -a $haveit$donthaveit$donthaveiteither != yesyesyes
 then
 	say "bug in test framework: multiple prerequisite tags do not work reliably"
 	exit 1
@@ -763,7 +763,7 @@ test_expect_success !LAZY_TRUE 'missing lazy prereqs skip tests' '
 	donthavetrue=no
 '
 
-if test "$havetrue$donthavetrue" != yesyes
+if test -z "$GIT_TEST_FAIL_PREREQS" -a "$havetrue$donthavetrue" != yesyes
 then
 	say 'bug in test framework: lazy prerequisites do not work'
 	exit 1
@@ -779,7 +779,7 @@ test_expect_success LAZY_FALSE 'missing negative lazy prereqs will skip' '
 	havefalse=no
 '
 
-if test "$nothavefalse$havefalse" != yesyes
+if test -z "$GIT_TEST_FAIL_PREREQS" -a "$nothavefalse$havefalse" != yesyes
 then
 	say 'bug in test framework: negative lazy prerequisites do not work'
 	exit 1
@@ -790,7 +790,7 @@ test_expect_success 'tests clean up after themselves' '
 	test_when_finished clean=yes
 '
 
-if test $clean != yes
+if test -z "$GIT_TEST_FAIL_PREREQS" -a $clean != yes
 then
 	say "bug in test framework: basic cleanup command does not work reliably"
 	exit 1
diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index 819c24d10e..c20209324c 100755
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh
@@ -352,7 +352,7 @@ test_expect_success 'log with grep.patternType configuration and command line' '
 	test_cmp expect actual
 '
 
-test_expect_success 'log with various grep.patternType configurations & command-lines' '
+test_expect_success !FAIL_PREREQS 'log with various grep.patternType configurations & command-lines' '
 	git init pattern-type &&
 	(
 		cd pattern-type &&
diff --git a/t/t7405-submodule-merge.sh b/t/t7405-submodule-merge.sh
index 7855bd8648..aa33978ed2 100755
--- a/t/t7405-submodule-merge.sh
+++ b/t/t7405-submodule-merge.sh
@@ -417,7 +417,7 @@ test_expect_failure 'directory/submodule conflict; keep submodule clean' '
 	)
 '
 
-test_expect_failure 'directory/submodule conflict; should not treat submodule files as untracked or in the way' '
+test_expect_failure !FAIL_PREREQS 'directory/submodule conflict; should not treat submodule files as untracked or in the way' '
 	test_when_finished "git -C directory-submodule/path reset --hard" &&
 	test_when_finished "git -C directory-submodule reset --hard" &&
 	(
diff --git a/t/t7810-grep.sh b/t/t7810-grep.sh
index 2e1bb61b41..7d7b396c23 100755
--- a/t/t7810-grep.sh
+++ b/t/t7810-grep.sh
@@ -412,7 +412,7 @@ do
 		test_cmp expected actual
 	'
 
-	test_expect_success !PCRE "grep $L with grep.patterntype=perl errors without PCRE" '
+	test_expect_success !FAIL_PREREQS,!PCRE "grep $L with grep.patterntype=perl errors without PCRE" '
 		test_must_fail git -c grep.patterntype=perl grep "foo.*bar"
 	'
 
@@ -1234,7 +1234,7 @@ test_expect_success PCRE 'grep --perl-regexp pattern' '
 	test_cmp expected actual
 '
 
-test_expect_success !PCRE 'grep --perl-regexp pattern errors without PCRE' '
+test_expect_success !FAIL_PREREQS,!PCRE 'grep --perl-regexp pattern errors without PCRE' '
 	test_must_fail git grep --perl-regexp "foo.*bar"
 '
 
@@ -1249,7 +1249,7 @@ test_expect_success LIBPCRE2 "grep -P with (*NO_JIT) doesn't error out" '
 
 '
 
-test_expect_success !PCRE 'grep -P pattern errors without PCRE' '
+test_expect_success !FAIL_PREREQS,!PCRE 'grep -P pattern errors without PCRE' '
 	test_must_fail git grep -P "foo.*bar"
 '
 
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 8270de74be..0367cec5fd 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -309,6 +309,26 @@ test_unset_prereq () {
 }
 
 test_set_prereq () {
+	if test -n "$GIT_TEST_FAIL_PREREQS"
+	then
+		case "$1" in
+		# The "!" case is handled below with
+		# test_unset_prereq()
+		!*)
+			;;
+		# (Temporary?) whitelist of things we can't easily
+		# pretend not to support
+		SYMLINKS)
+			;;
+		# Inspecting whether GIT_TEST_FAIL_PREREQS is on
+		# should be unaffected.
+		FAIL_PREREQS)
+			;;
+		*)
+			return
+		esac
+	fi
+
 	case "$1" in
 	!*)
 		test_unset_prereq "${1#!}"
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 599fd70e14..4b346467df 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -1607,3 +1607,7 @@ test_lazy_prereq SHA1 '
 test_lazy_prereq REBASE_P '
 	test -z "$GIT_TEST_SKIP_REBASE_P"
 '
+
+test_lazy_prereq FAIL_PREREQS '
+	test -n "$GIT_TEST_FAIL_PREREQS"
+'