From d8e758387ca3e61d9d22bd3873568f282ed7a187 Mon Sep 17 00:00:00 2001
From: Sven van Heugten <sven@memcmp.org>
Date: Wed, 4 Mar 2026 07:22:46 +0100
Subject: [PATCH] Add partial change example

```git-check-assertions
sed -i 's/HEAD~/HEAD/' test/git-check-assertions.bats
run test/git-check-assertions.bats
assert_failure
assert_output --partial "Expected command to fail, but it succeeded."
```
---
 README.md                      | 11 +++++++++++
 test/git-check-assertions.bats | 16 ++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/README.md b/README.md
index 3eb57c4..f1cfb95 100644
--- a/README.md
+++ b/README.md
@@ -125,3 +125,14 @@ run dotnet test --no-build
 assert_failure
 ```
 ~~~
+
+Assert that a specific change in a commit is necessary for the tests to succeed:
+
+~~~
+```git-check-assertions
+git checkout HEAD~ Main.fs
+run dotnet test
+assert_failure
+assert_output --partial "Invalid URL"
+```
+~~~
diff --git a/test/git-check-assertions.bats b/test/git-check-assertions.bats
index 697d47d..2e45490 100755
--- a/test/git-check-assertions.bats
+++ b/test/git-check-assertions.bats
@@ -113,6 +113,22 @@ commit_with_assertion() {
   assert_success
 }
 
+@test "you can use git checkout in an assertion to assert against a mixed version of the code" {
+  git checkout -b feature
+  echo hello >src
+  echo 'grep hello src' >tests
+  git add src tests
+  git commit -m 'add src and tests'
+  echo goodbye >src
+  echo 'grep goodbye src' >tests
+  git add src tests
+  commit_with_assertion $'git checkout HEAD~ src\nrun bash tests\nassert_failure'
+
+  run git-check-assertions
+
+  assert_success
+}
+
 @test "assert_success should succeed if the executed command succeeded" {
   git checkout -b feature
   commit_with_assertion $'run exit 0\nassert_success'