const-oid: add basic proptests

Exercises the parser beyond what we currently do in unit tests

const-oid/Cargo.toml

@@ -22,6 +22,7 @@ arbitrary = { version = "1.2", optional = true, features = ["derive"] }
 
 [dev-dependencies]
 hex-literal = "0.4"
+proptest = "1"
 
 [features]
 db = []

const-oid/tests/proptests.proptest-regressions

@@ -0,0 +1,7 @@
+# Seeds for failure cases proptest has generated in the past. It is
+# automatically read and these particular cases re-run before any
+# novel cases are generated.
+#
+# It is recommended to check this file in to source control so that
+# everyone who runs the test benefits from these saved cases.
+cc 1663923d2fb0c804c5b850d10dd0ded1cbfc06dddf3f88faa4abf149b8430831 # shrinks to s = ""

const-oid/tests/proptests.rs

@@ -0,0 +1,43 @@
+//! `proptest`-powered property-based tests.
+
+use const_oid::ObjectIdentifier;
+use proptest::prelude::*;
+
+prop_compose! {
+    /// Produce a string of digits and dots, i.e. the component parts of OIDs.
+    ///
+    /// Note that this can be any permutation of digits-and-dots and does not necessarily
+    /// represent a valid OID.
+    fn oid_like_string()(bytes in any::<Vec<u8>>()) -> String {
+        // Create a digit or dot from a byte input
+        fn byte_to_char(byte: u8) -> char {
+            match byte % 11 {
+                n @ 0..=9  => (b'0' + n) as char,
+                10 => '.',
+                _ => unreachable!()
+            }
+        }
+
+
+        let mut ret = String::with_capacity(bytes.len());
+        for byte in bytes {
+            ret.push(byte_to_char(byte));
+        }
+        ret
+    }
+}
+
+proptest! {
+    #[test]
+    fn round_trip(s in oid_like_string()) {
+        match ObjectIdentifier::new(&s) {
+            Ok(oid) => {
+                let oid_string = oid.to_string();
+                prop_assert_eq!(s, oid_string);
+            },
+            Err(_e) => {
+                // TODO(tarcieri): use a regex or some other method to ensure the OID is invalid
+            }
+        }
+    }
+}