Add test for BTC/kb conversion

Add a test to check that we can convert 0.000001 BTC/kB to sats i.e.,
100 sats per kB (note naive div / 1000 truncates to zero).

Author: tcharding

types/src/lib.rs

@@ -288,3 +288,16 @@ impl ScriptSig {
         ScriptBuf::from_hex(&self.hex)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn convert_btc_per_kb() {
+        // per kB = per kvB because this is a conversion of legacy transaction weights.
+        let f: f64 = 0.000001;
+        let got = btc_per_kb(f).unwrap();
+        assert_eq!(got, Some(FeeRate::from_sat_per_kwu(25)))
+    }
+}