Add arbitrary trait implementation

ethereum-types/Cargo.toml

@@ -22,3 +22,4 @@ serde_json = "1.0.41"
 default = ["std", "serialize"]
 std = ["uint-crate/std", "fixed-hash/std", "ethbloom/std", "primitive-types/std"]
 serialize = ["std", "impl-serde", "primitive-types/serde", "ethbloom/serialize"]
+arbitrary = ["std", "serialize", "fixed-hash/arbitrary"]

fixed-hash/Cargo.toml

@@ -19,6 +19,7 @@ quickcheck = { version = "0.9.0", optional = true }
 rand = { version = "0.7.2", optional = true, default-features = false }
 rustc-hex = { version = "2.0.1", optional = true, default-features = false }
 static_assertions = "1.0.0"
+arbitrary = { version = "0.4", optional = true }
 
 [dev-dependencies]
 rand_xorshift = "0.2.0"

fixed-hash/src/hash.rs

@@ -316,6 +316,7 @@ macro_rules! construct_fixed_hash {
 		impl_cmp_for_fixed_hash!($name);
 		impl_rustc_hex_for_fixed_hash!($name);
 		impl_quickcheck_for_fixed_hash!($name);
+		impl_arbitrary_for_fixed_hash!($name);
 	}
 }
 
@@ -636,6 +637,42 @@ macro_rules! impl_quickcheck_for_fixed_hash {
 	};
 }
 
+// Implementation for disabled `arbitrary` crate support.
+//
+// # Note
+//
+// Feature guarded macro definitions instead of feature guarded impl blocks
+// to work around the problems of introducing `arbitrary` crate feature in
+// a user crate.
+#[cfg(not(feature = "arbitrary"))]
+#[macro_export]
+#[doc(hidden)]
+macro_rules! impl_arbitrary_for_fixed_hash {
+	( $name:ident ) => {};
+}
+
+// Implementation for enabled `arbitrary` crate support.
+//
+// # Note
+//
+// Feature guarded macro definitions instead of feature guarded impl blocks
+// to work around the problems of introducing `arbitrary` crate feature in
+// a user crate.
+#[cfg(feature = "arbitrary")]
+#[macro_export]
+#[doc(hidden)]
+macro_rules! impl_arbitrary_for_fixed_hash {
+	( $name:ident ) => {
+		impl $crate::arbitrary::Arbitrary for $name {
+			fn arbitrary(u: &mut $crate::arbitrary::Unstructured<'_>) -> $crate::arbitrary::Result<Self> {
+				let mut res = Self::zero();
+				u.fill_buffer(&mut res.0)?;
+				Ok(Self::from(res))
+			}
+		}
+	};
+}
+
 #[macro_export]
 #[doc(hidden)]
 macro_rules! impl_ops_for_hash {

fixed-hash/src/lib.rs

@@ -46,6 +46,10 @@ pub use rand;
 #[doc(hidden)]
 pub use quickcheck;
 
+#[cfg(feature = "arbitrary")]
+#[doc(hidden)]
+pub use arbitrary;
+
 #[macro_use]
 mod hash;