Merge rust-bitcoin/rust-bitcoin#4287: units: Kill mutants found in weekly mutation testing

f15e461baf Add an exclusion for a mutant in a deprecated fn (Jamil Lambert, PhD)
9a2b56f381 Modify test in Amount to kill mutants (Jamil Lambert, PhD)
1d1cf00b1e Add test to BlockTime to kill mutants (Jamil Lambert, PhD)

Pull request description:

  Weekly mutation testing found mutants in `Amount` and `BlockTime`.

  Add a test to `BlockTime`.
  Add two asserts to `Amount` tests.
  Exclude deprecated function from mutation testing.

  Closes #4225, #4243, #4278

ACKs for top commit:
  apoelstra:
    ACK f15e461baf463da0bf9d89018180c1d5032106c1; successfully ran local tests

Tree-SHA512: 18a405362db1b2eabac7c7ac01a56d306a1bf5f705626b5c217ec329e6420daa2f2e62b37c72537f29b7ee76b9fd795adde2da71b226fec3a74d0f25dca6cd96

.cargo/mutants.toml

@@ -21,6 +21,7 @@ exclude_re = [
     "Time::to_consensus_u32", # Mutant from replacing | with ^, this returns the same value since the XOR is taken against the u16 with an all-zero bitmask
     "FeeRate::fee_vb", # Deprecated
     "FeeRate::fee_wu", # Deprecated
+    "SignedAmount::checked_abs", # Deprecated
 
     # primitives
     "Sequence::from_512_second_intervals", # Mutant from replacing | with ^, this returns the same value since the XOR is taken against the u16 with an all-zero bitmask

units/src/amount/tests.rs

@@ -104,8 +104,13 @@ fn from_str_zero_without_denomination() {
 fn from_int_btc() {
     let amt = Amount::from_btc_u16(2);
     assert_eq!(sat(200_000_000), amt);
+    let amt = Amount::from_int_btc(2_u16);
+    assert_eq!(sat(200_000_000), amt);
+
     let amt = SignedAmount::from_btc_i16(-2);
     assert_eq!(ssat(-200_000_000), amt);
+    let amt = SignedAmount::from_int_btc(-2_i16);
+    assert_eq!(ssat(-200_000_000), amt);
 }
 
 #[test]

units/src/time.rs

@@ -56,3 +56,14 @@ impl<'a> Arbitrary<'a> for BlockTime {
         Ok(BlockTime::from(t))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn block_time_round_trip() {
+        let t = BlockTime::from(1_742_979_600); // 26 Mar 2025 9:00 UTC
+        assert_eq!(u32::from(t), 1_742_979_600);
+    }
+}