diff --git a/build_system/src/fmt.rs b/build_system/src/fmt.rs
index 7e6594f50f9..91535f217e3 100644
--- a/build_system/src/fmt.rs
+++ b/build_system/src/fmt.rs
@@ -1,7 +1,7 @@
 use std::ffi::OsStr;
 use std::path::Path;
 
-use crate::utils::run_command_with_output;
+use crate::utils::{run_command_with_output, walk_dir};
 
 fn show_usage() {
     println!(
@@ -32,5 +32,31 @@ pub fn run() -> Result<(), String> {
         if check { &[&"cargo", &"fmt", &"--check"] } else { &[&"cargo", &"fmt"] };
 
     run_command_with_output(cmd, Some(Path::new(".")))?;
-    run_command_with_output(cmd, Some(Path::new("build_system")))
+    run_command_with_output(cmd, Some(Path::new("build_system")))?;
+
+    run_rustfmt_recursively("tests/run", check)
+}
+
+fn run_rustfmt_recursively<P>(dir: P, check: bool) -> Result<(), String>
+where
+    P: AsRef<Path>,
+{
+    walk_dir(
+        dir,
+        &mut |dir| run_rustfmt_recursively(dir, check),
+        &mut |file_path| {
+            if file_path.extension().filter(|ext| ext == &OsStr::new("rs")).is_some() {
+                let rustfmt_cmd: &[&dyn AsRef<OsStr>] = if check {
+                    &[&"rustfmt", &"--check", &file_path]
+                } else {
+                    &[&"rustfmt", &file_path]
+                };
+
+                run_command_with_output(rustfmt_cmd, Some(Path::new(".")))
+            } else {
+                Ok(())
+            }
+        },
+        true,
+    )
 }
diff --git a/tests/run/int.rs b/tests/run/int.rs
index e20ecc23679..78675acb544 100644
--- a/tests/run/int.rs
+++ b/tests/run/int.rs
@@ -7,12 +7,10 @@ fn main() {
     use std::hint::black_box;
 
     macro_rules! check {
-        ($ty:ty, $expr:expr) => {
-            {
-                const EXPECTED: $ty = $expr;
-                assert_eq!($expr, EXPECTED);
-            }
-        };
+        ($ty:ty, $expr:expr) => {{
+            const EXPECTED: $ty = $expr;
+            assert_eq!($expr, EXPECTED);
+        }};
     }
 
     check!(u32, (2220326408_u32 + black_box(1)) >> (32 - 6));
diff --git a/tests/run/int_overflow.rs b/tests/run/int_overflow.rs
index 78872159f62..78e1cac57e0 100644
--- a/tests/run/int_overflow.rs
+++ b/tests/run/int_overflow.rs
@@ -12,7 +12,7 @@ fn main() {
 
     let arg_count = std::env::args().count();
     let int = isize::MAX;
-    let _int = int + arg_count as isize;  // overflow
+    let _int = int + arg_count as isize; // overflow
 
     // If overflow checking is disabled, we should reach here.
     #[cfg(not(debug_assertions))]
diff --git a/tests/run/structs.rs b/tests/run/structs.rs
index da73cbed9ae..e08e67837be 100644
--- a/tests/run/structs.rs
+++ b/tests/run/structs.rs
@@ -27,12 +27,8 @@ fn one() -> isize {
 
 #[no_mangle]
 extern "C" fn main(argc: i32, _argv: *const *const u8) -> i32 {
-    let test = Test {
-        field: one(),
-    };
-    let two = Two {
-        two: 2,
-    };
+    let test = Test { field: one() };
+    let two = Two { two: 2 };
     unsafe {
         libc::printf(b"%ld\n\0" as *const u8 as *const i8, test.field);
         libc::printf(b"%ld\n\0" as *const u8 as *const i8, two.two);
diff --git a/tests/run/volatile.rs b/tests/run/volatile.rs
index 94a7bdc5c06..dc11fbfa600 100644
--- a/tests/run/volatile.rs
+++ b/tests/run/volatile.rs
@@ -12,15 +12,11 @@ struct Struct {
     func: unsafe fn(*const ()),
 }
 
-fn func(_ptr: *const ()) {
-}
+fn func(_ptr: *const ()) {}
 
 fn main() {
     let mut x = MaybeUninit::<&Struct>::uninit();
-    x.write(&Struct {
-        pointer: std::ptr::null(),
-        func,
-    });
+    x.write(&Struct { pointer: std::ptr::null(), func });
     let x = unsafe { x.assume_init() };
     let value = unsafe { (x as *const Struct).read_volatile() };
     println!("{:?}", value);
diff --git a/tests/run/volatile2.rs b/tests/run/volatile2.rs
index bdcb8259878..ada112687d3 100644
--- a/tests/run/volatile2.rs
+++ b/tests/run/volatile2.rs
@@ -7,7 +7,14 @@ mod libc {
     #[link(name = "c")]
     extern "C" {
         pub fn sigaction(signum: i32, act: *const sigaction, oldact: *mut sigaction) -> i32;
-        pub fn mmap(addr: *mut (), len: usize, prot: i32, flags: i32, fd: i32, offset: i64) -> *mut ();
+        pub fn mmap(
+            addr: *mut (),
+            len: usize,
+            prot: i32,
+            flags: i32,
+            fd: i32,
+            offset: i64,
+        ) -> *mut ();
         pub fn mprotect(addr: *mut (), len: usize, prot: i32) -> i32;
     }
 
@@ -54,7 +61,8 @@ fn main() {
             libc::MAP_PRIVATE | libc::MAP_ANONYMOUS,
             -1,
             0,
-        ).cast();
+        )
+        .cast();
         if STORAGE == libc::MAP_FAILED {
             panic!("error: mmap failed");
         }