diff --git a/check_diff/src/lib.rs b/check_diff/src/lib.rs
index 9d3cc906a93..d3f1dfa7278 100644
--- a/check_diff/src/lib.rs
+++ b/check_diff/src/lib.rs
@@ -114,7 +114,7 @@ impl RustfmtRunner {
     // code: Code to run the binary on
     // config: Any additional configuration options to pass to rustfmt
     //
-    fn format_code<'a>(
+    pub fn format_code<'a>(
         &self,
         code: &'a str,
         config: &Option<Vec<String>>,
@@ -346,7 +346,7 @@ pub fn compile_rustfmt(
     });
 }
 
-fn search_for_rs_files(repo: &Path) -> impl Iterator<Item = PathBuf> {
+pub fn search_for_rs_files(repo: &Path) -> impl Iterator<Item = PathBuf> {
     return WalkDir::new(repo).into_iter().filter_map(|e| match e.ok() {
         Some(entry) => {
             let path = entry.path();
diff --git a/check_diff/tests/check_diff.rs b/check_diff/tests/check_diff.rs
new file mode 100644
index 00000000000..3531508f229
--- /dev/null
+++ b/check_diff/tests/check_diff.rs
@@ -0,0 +1,80 @@
+use check_diff::{check_diff, compile_rustfmt, search_for_rs_files, CheckDiffError};
+use std::fs::File;
+use tempfile::Builder;
+
+#[test]
+fn search_for_files_correctly_non_nested() -> Result<(), Box<dyn std::error::Error>> {
+    let dir = Builder::new().tempdir_in("").unwrap();
+    let file_path = dir.path().join("test.rs");
+    let _tmp_file = File::create(file_path)?;
+
+    let iter = search_for_rs_files(dir.path());
+
+    let mut count = 0;
+    for _ in iter {
+        count += 1;
+    }
+
+    assert_eq!(count, 1);
+
+    Ok(())
+}
+
+#[test]
+fn search_for_files_correctly_nested() -> Result<(), Box<dyn std::error::Error>> {
+    let dir = Builder::new().tempdir_in("").unwrap();
+    let file_path = dir.path().join("test.rs");
+    let _tmp_file = File::create(file_path)?;
+
+    let nested_dir = Builder::new().tempdir_in(dir.path()).unwrap();
+    let nested_file_path = nested_dir.path().join("nested.rs");
+    let _ = File::create(nested_file_path)?;
+
+    let iter = search_for_rs_files(dir.path());
+
+    let mut count = 0;
+    for _ in iter {
+        count += 1;
+    }
+
+    assert_eq!(count, 2);
+
+    Ok(())
+}
+
+#[test]
+fn check_diff_test() -> Result<(), CheckDiffError> {
+    let tmp_dir = Builder::new().tempdir_in("").unwrap();
+    let runners = compile_rustfmt(
+        tmp_dir.path(),
+        "https://github.com/rust-lang/rustfmt".to_string(),
+        "rustfmt-1.4.32".to_string(),
+        None,
+    )?;
+
+    let dir = Builder::new().tempdir_in("").unwrap();
+    let file_path = dir.path().join("test.rs");
+    let _tmp_file = File::create(file_path)?;
+
+    let errors = check_diff(None, runners, dir.path());
+    assert_eq!(errors, 0);
+    Ok(())
+}
+
+#[test]
+fn format_simple_code() -> Result<(), CheckDiffError> {
+    let tmp_dir = Builder::new().tempdir_in("").unwrap();
+    let runners = compile_rustfmt(
+        tmp_dir.path(),
+        "https://github.com/rust-lang/rustfmt".to_string(),
+        "rustfmt-1.4.32".to_string(),
+        None,
+    )?;
+
+    let output = runners
+        .src_runner
+        .format_code("fn main()              {}", &None)?;
+    assert_eq!(output, "fn main() {}\n".to_string());
+
+    Ok(())
+}
diff --git a/check_diff/tests/diffy.rs b/check_diff/tests/diffy.rs
deleted file mode 100644
index 03157c8f487..00000000000
--- a/check_diff/tests/diffy.rs
+++ /dev/null
@@ -1,22 +0,0 @@
-use diffy::{self, create_patch};
-
-#[test]
-fn diffy_test_diff() {
-    let original = "The quick brown fox jumps over the lazy dog";
-    let modified = "The quick brown fox jumps over the LAZY dog";
-
-    let patch = create_patch(original, modified);
-    // diffy uses hunks which indicates the lines that are different
-    assert_eq!(patch.hunks().is_empty(), false);
-    // hence regardless, patch.to_string() will never be empty
-    assert_eq!(patch.to_string().is_empty(), false);
-}
-
-#[test]
-fn diffy_test_no_diff() {
-    let original = "The quick brown fox jumps over the lazy dog";
-
-    let patch = create_patch(original, original);
-    assert_eq!(patch.hunks().is_empty(), true);
-    assert_eq!(patch.to_string().is_empty(), false);
-}