rust: str: take advantage of the -> Result support in KUnit #[test]'s

Since now we have support for returning `-> Result`s, we can convert some
of these tests to use the feature, and serve as a first user for it too.

Thus convert them, which allows us to remove some `unwrap()`s.

We keep the actual assertions we want to make as explicit ones with
`assert*!`s.

Reviewed-by: David Gow <davidgow@google.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20250502215133.1923676-6-ojeda@kernel.org
[ Split the `CString` simplification into a new commit. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: ojeda

rust/kernel/str.rs

@@ -578,7 +578,7 @@ mod tests {
 
     macro_rules! format {
         ($($f:tt)*) => ({
-            CString::try_from_fmt(::kernel::fmt!($($f)*)).unwrap().to_str().unwrap()
+            CString::try_from_fmt(::kernel::fmt!($($f)*))?.to_str()?
         })
     }
 
@@ -597,66 +597,72 @@ mod tests {
         \\xf0\\xf1\\xf2\\xf3\\xf4\\xf5\\xf6\\xf7\\xf8\\xf9\\xfa\\xfb\\xfc\\xfd\\xfe\\xff";
 
     #[test]
-    fn test_cstr_to_str() {
+    fn test_cstr_to_str() -> Result {
         let good_bytes = b"\xf0\x9f\xa6\x80\0";
-        let checked_cstr = CStr::from_bytes_with_nul(good_bytes).unwrap();
-        let checked_str = checked_cstr.to_str().unwrap();
+        let checked_cstr = CStr::from_bytes_with_nul(good_bytes)?;
+        let checked_str = checked_cstr.to_str()?;
         assert_eq!(checked_str, "🦀");
+        Ok(())
     }
 
     #[test]
-    fn test_cstr_to_str_invalid_utf8() {
+    fn test_cstr_to_str_invalid_utf8() -> Result {
         let bad_bytes = b"\xc3\x28\0";
-        let checked_cstr = CStr::from_bytes_with_nul(bad_bytes).unwrap();
+        let checked_cstr = CStr::from_bytes_with_nul(bad_bytes)?;
         assert!(checked_cstr.to_str().is_err());
+        Ok(())
     }
 
     #[test]
-    fn test_cstr_as_str_unchecked() {
+    fn test_cstr_as_str_unchecked() -> Result {
         let good_bytes = b"\xf0\x9f\x90\xA7\0";
-        let checked_cstr = CStr::from_bytes_with_nul(good_bytes).unwrap();
+        let checked_cstr = CStr::from_bytes_with_nul(good_bytes)?;
         // SAFETY: The contents come from a string literal which contains valid UTF-8.
         let unchecked_str = unsafe { checked_cstr.as_str_unchecked() };
         assert_eq!(unchecked_str, "🐧");
+        Ok(())
     }
 
     #[test]
-    fn test_cstr_display() {
-        let hello_world = CStr::from_bytes_with_nul(b"hello, world!\0").unwrap();
+    fn test_cstr_display() -> Result {
+        let hello_world = CStr::from_bytes_with_nul(b"hello, world!\0")?;
         assert_eq!(format!("{hello_world}"), "hello, world!");
-        let non_printables = CStr::from_bytes_with_nul(b"\x01\x09\x0a\0").unwrap();
+        let non_printables = CStr::from_bytes_with_nul(b"\x01\x09\x0a\0")?;
         assert_eq!(format!("{non_printables}"), "\\x01\\x09\\x0a");
-        let non_ascii = CStr::from_bytes_with_nul(b"d\xe9j\xe0 vu\0").unwrap();
+        let non_ascii = CStr::from_bytes_with_nul(b"d\xe9j\xe0 vu\0")?;
         assert_eq!(format!("{non_ascii}"), "d\\xe9j\\xe0 vu");
-        let good_bytes = CStr::from_bytes_with_nul(b"\xf0\x9f\xa6\x80\0").unwrap();
+        let good_bytes = CStr::from_bytes_with_nul(b"\xf0\x9f\xa6\x80\0")?;
         assert_eq!(format!("{good_bytes}"), "\\xf0\\x9f\\xa6\\x80");
+        Ok(())
     }
 
     #[test]
-    fn test_cstr_display_all_bytes() {
+    fn test_cstr_display_all_bytes() -> Result {
         let mut bytes: [u8; 256] = [0; 256];
         // fill `bytes` with [1..=255] + [0]
         for i in u8::MIN..=u8::MAX {
             bytes[i as usize] = i.wrapping_add(1);
         }
-        let cstr = CStr::from_bytes_with_nul(&bytes).unwrap();
+        let cstr = CStr::from_bytes_with_nul(&bytes)?;
         assert_eq!(format!("{cstr}"), ALL_ASCII_CHARS);
+        Ok(())
     }
 
     #[test]
-    fn test_cstr_debug() {
-        let hello_world = CStr::from_bytes_with_nul(b"hello, world!\0").unwrap();
+    fn test_cstr_debug() -> Result {
+        let hello_world = CStr::from_bytes_with_nul(b"hello, world!\0")?;
         assert_eq!(format!("{hello_world:?}"), "\"hello, world!\"");
-        let non_printables = CStr::from_bytes_with_nul(b"\x01\x09\x0a\0").unwrap();
+        let non_printables = CStr::from_bytes_with_nul(b"\x01\x09\x0a\0")?;
         assert_eq!(format!("{non_printables:?}"), "\"\\x01\\x09\\x0a\"");
-        let non_ascii = CStr::from_bytes_with_nul(b"d\xe9j\xe0 vu\0").unwrap();
+        let non_ascii = CStr::from_bytes_with_nul(b"d\xe9j\xe0 vu\0")?;
         assert_eq!(format!("{non_ascii:?}"), "\"d\\xe9j\\xe0 vu\"");
-        let good_bytes = CStr::from_bytes_with_nul(b"\xf0\x9f\xa6\x80\0").unwrap();
+        let good_bytes = CStr::from_bytes_with_nul(b"\xf0\x9f\xa6\x80\0")?;
         assert_eq!(format!("{good_bytes:?}"), "\"\\xf0\\x9f\\xa6\\x80\"");
+        Ok(())
     }
 
     #[test]
-    fn test_bstr_display() {
+    fn test_bstr_display() -> Result {
         let hello_world = BStr::from_bytes(b"hello, world!");
         assert_eq!(format!("{hello_world}"), "hello, world!");
         let escapes = BStr::from_bytes(b"_\t_\n_\r_\\_\'_\"_");
@@ -667,10 +673,11 @@ mod tests {
         assert_eq!(format!("{non_ascii}"), "d\\xe9j\\xe0 vu");
         let good_bytes = BStr::from_bytes(b"\xf0\x9f\xa6\x80");
         assert_eq!(format!("{good_bytes}"), "\\xf0\\x9f\\xa6\\x80");
+        Ok(())
     }
 
     #[test]
-    fn test_bstr_debug() {
+    fn test_bstr_debug() -> Result {
         let hello_world = BStr::from_bytes(b"hello, world!");
         assert_eq!(format!("{hello_world:?}"), "\"hello, world!\"");
         let escapes = BStr::from_bytes(b"_\t_\n_\r_\\_\'_\"_");
@@ -681,6 +688,7 @@ mod tests {
         assert_eq!(format!("{non_ascii:?}"), "\"d\\xe9j\\xe0 vu\"");
         let good_bytes = BStr::from_bytes(b"\xf0\x9f\xa6\x80");
         assert_eq!(format!("{good_bytes:?}"), "\"\\xf0\\x9f\\xa6\\x80\"");
+        Ok(())
     }
 }