diff --git a/Cargo.toml b/Cargo.toml
index 181ec13..31ec604 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,3 +16,8 @@ targets = ["x86_64-unknown-linux-gnu"]
 
 [target.'cfg(any(target_os = "macos", target_os = "ios", target_os = "freebsd"))'.dependencies]
 libc = "0.2.107"
+
+[[test]]
+name = "tests"
+path = "tests.rs"
+harness = false
diff --git a/src/lib.rs b/src/lib.rs
index e54a652..b7361fa 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -18,56 +18,3 @@ pub fn num_threads() -> Option<NonZeroUsize> {
 pub fn is_single_threaded() -> Option<bool> {
     num_threads().map(|n| n.get() == 1)
 }
-
-#[cfg(test)]
-mod test {
-    use std::num::NonZeroUsize;
-
-    // Run each expression in its own thread.
-    macro_rules! threaded {
-        ($first:expr;) => {
-            $first;
-        };
-        ($first:expr; $($rest:expr;)*) => {
-            $first;
-            ::std::thread::spawn(|| {
-                threaded!($($rest;)*);
-            })
-            .join()
-            .unwrap();
-        };
-    }
-
-    #[test]
-    fn require_test_threads_1() {
-        if super::is_single_threaded() != Some(true) {
-            panic!(
-                "Process is not single-threaded. Are you running `cargo test -- --test-threads=1`?"
-            );
-        }
-    }
-
-    #[test]
-    fn num_threads() {
-        threaded! {
-            assert_eq!(super::num_threads().map(NonZeroUsize::get), Some(1));
-            assert_eq!(super::num_threads().map(NonZeroUsize::get), Some(2));
-            assert_eq!(super::num_threads().map(NonZeroUsize::get), Some(3));
-            assert_eq!(super::num_threads().map(NonZeroUsize::get), Some(4));
-            assert_eq!(super::num_threads().map(NonZeroUsize::get), Some(5));
-            assert_eq!(super::num_threads().map(NonZeroUsize::get), Some(6));
-        }
-    }
-
-    #[test]
-    fn is_single_threaded() {
-        threaded! {
-            assert_eq!(super::is_single_threaded(), Some(true));
-            assert_eq!(super::is_single_threaded(), Some(false));
-            assert_eq!(super::is_single_threaded(), Some(false));
-            assert_eq!(super::is_single_threaded(), Some(false));
-            assert_eq!(super::is_single_threaded(), Some(false));
-            assert_eq!(super::is_single_threaded(), Some(false));
-        }
-    }
-}
diff --git a/tests.rs b/tests.rs
new file mode 100644
index 0000000..3e88243
--- /dev/null
+++ b/tests.rs
@@ -0,0 +1,57 @@
+extern crate num_threads;
+
+use std::num::NonZeroUsize;
+
+use num_threads::*;
+
+// Run each expression in its own thread.
+macro_rules! threaded {
+    ($first:expr;) => {
+        $first;
+    };
+    ($first:expr; $($rest:expr;)*) => {
+        $first;
+        ::std::thread::spawn(|| {
+            threaded!($($rest;)*);
+        })
+        .join()
+        .unwrap();
+    };
+}
+
+fn test_single_threaded_by_default() {
+    if is_single_threaded() != Some(true) {
+        panic!("Process is not single-threaded, but it should be.");
+    }
+}
+
+fn test_num_threads() {
+    threaded! {
+        assert_eq!(num_threads().map(NonZeroUsize::get), Some(1));
+        assert_eq!(num_threads().map(NonZeroUsize::get), Some(2));
+        assert_eq!(num_threads().map(NonZeroUsize::get), Some(3));
+        assert_eq!(num_threads().map(NonZeroUsize::get), Some(4));
+        assert_eq!(num_threads().map(NonZeroUsize::get), Some(5));
+        assert_eq!(num_threads().map(NonZeroUsize::get), Some(6));
+    }
+}
+
+fn test_is_single_threaded() {
+    threaded! {
+        assert_eq!(is_single_threaded(), Some(true));
+        assert_eq!(is_single_threaded(), Some(false));
+        assert_eq!(is_single_threaded(), Some(false));
+        assert_eq!(is_single_threaded(), Some(false));
+        assert_eq!(is_single_threaded(), Some(false));
+        assert_eq!(is_single_threaded(), Some(false));
+    }
+}
+
+fn main() {
+    test_single_threaded_by_default();
+    std::thread::sleep(std::time::Duration::new(0, 100));
+    test_num_threads();
+    std::thread::sleep(std::time::Duration::new(0, 100));
+    test_is_single_threaded();
+    eprintln!("All tests passed!");
+}