diff --git a/README.md b/README.md
index 7fdbb0c..ab9e051 100644
--- a/README.md
+++ b/README.md
@@ -28,6 +28,9 @@ $ make prepare-test
 ```
 
 7. Check the functions of `joj3` with the `make test`, which should pass all the test cases. The cases used here are in `/examples`.
+
+Note: you may fail the test if the checking tools are not installed. e.g. For the test case `cpplint/sillycode`, you need to install `cpplint` in `/usr/bin` or `/usr/local/bin`.
+
 ```bash
 $ make test
 go test -coverprofile cover.out -v ./...