riscv: add misa unit tests

Adds basic unit tests for the `misa` register.

Author: rmsyn

riscv/CHANGELOG.md

@@ -21,6 +21,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Use CSR helper macros to define `mcounteren` register
 - Use CSR helper macros to define `mie` register
 - Use CSR helper macros to define `mimpid` register
+- Use CSR helper macros to define `misa` register
 
 ## [v0.12.1] - 2024-10-20
 

riscv/src/register/misa.rs

@@ -65,3 +65,30 @@ impl Misa {
 const fn ext_char_to_bit(extension: char) -> u8 {
     (extension as u8).saturating_sub('A' as u8)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::result::Error;
+
+    #[test]
+    fn test_misa() {
+        (1..=3).zip([XLEN::XLEN32, XLEN::XLEN64, XLEN::XLEN128]).for_each(|(raw, exp_xlen)| {
+            assert_eq!(XLEN::try_from(raw), Ok(exp_xlen));
+            assert_eq!(usize::from(exp_xlen), raw);
+
+            let misa = Misa::from_bits(raw << (usize::BITS - 2));
+            assert_eq!(misa.try_mxl(), Ok(exp_xlen));
+            assert_eq!(misa.mxl(), exp_xlen);
+        });
+
+        (0..62).map(|b| 1 << b).for_each(|invalid_mxl| {
+            assert_eq!(Misa::from_bits(invalid_mxl).try_mxl(), Err(Error::InvalidVariant(0)));
+        });
+
+        ('A'..='Z').for_each(|ext| {
+            assert!(!Misa::from_bits(0).has_extension(ext));
+            assert!(Misa::from_bits(1 << ext_char_to_bit(ext)).has_extension(ext));
+        });
+    }
+}