Add tests for SemVer parsing

src/semver.rs

@@ -85,3 +85,34 @@ impl PartialOrd for SemVer {
         Some(self.cmp(other))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::num::NonZeroU16;
+
+    use super::*;
+
+    #[test]
+    fn from_str() {
+        let mut s: SemVer = "1.2.3".parse().unwrap();
+        assert_eq!(
+            s,
+            SemVer {
+                major: 1,
+                minor: 2,
+                patch: 3,
+                pre: PreRelease::None,
+            }
+        );
+        s = "0.3.0_alpha4".parse().unwrap();
+        assert_eq!(
+            s,
+            SemVer {
+                major: 0,
+                minor: 3,
+                patch: 0,
+                pre: PreRelease::Alpha(Some(NonZeroU16::new(4).unwrap())),
+            }
+        )
+    }
+}