rust: add example unit tests

For both `kernel` and `macros`, so that we know unit tests
actually run & work.

Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: ojeda

rust/kernel/sysctl.rs

@@ -184,3 +184,15 @@ impl<T: SysctlStorage> Drop for Sysctl<T> {
         self.header = ptr::null_mut();
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_trim_whitespace() {
+        assert_eq!(trim_whitespace(b"foo    "), b"foo");
+        assert_eq!(trim_whitespace(b"    foo"), b"foo");
+        assert_eq!(trim_whitespace(b"  foo  "), b"foo");
+    }
+}

rust/macros/module.rs

@@ -741,3 +741,32 @@ pub fn module_misc_device(ts: TokenStream) -> TokenStream {
     .parse()
     .expect("Error parsing formatted string into token stream.")
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_permissions_are_readonly() {
+        assert!(permissions_are_readonly("0b000000000"));
+        assert!(permissions_are_readonly("0o000"));
+        assert!(permissions_are_readonly("000"));
+        assert!(permissions_are_readonly("0x000"));
+
+        assert!(!permissions_are_readonly("0b111111111"));
+        assert!(!permissions_are_readonly("0o777"));
+        assert!(!permissions_are_readonly("511"));
+        assert!(!permissions_are_readonly("0x1ff"));
+
+        assert!(permissions_are_readonly("0o014"));
+        assert!(permissions_are_readonly("0o015"));
+
+        assert!(!permissions_are_readonly("0o214"));
+        assert!(!permissions_are_readonly("0o024"));
+        assert!(!permissions_are_readonly("0o012"));
+
+        assert!(!permissions_are_readonly("0o315"));
+        assert!(!permissions_are_readonly("0o065"));
+        assert!(!permissions_are_readonly("0o017"));
+    }
+}