gnu: Add rust-toml-test-harness-0.4.

* gnu/packages/crates-io.scm (rust-toml-test-harness-0.4): New variable.

gnu/packages/crates-io.scm

@@ -64039,6 +64039,28 @@ parser.")
          ("rust-pretty-assertions" ,rust-pretty-assertions-1)
          ("rust-snapbox" ,rust-snapbox-0.2))))))
 
+(define-public rust-toml-test-harness-0.4
+  (package
+    (name "rust-toml-test-harness")
+    (version "0.4.3")
+    (source (origin
+              (method url-fetch)
+              (uri (crate-uri "toml-test-harness" version))
+              (file-name (string-append name "-" version ".tar.gz"))
+              (sha256
+               (base32 "0xgn9a7q3s46fdxw6jajcbwxc0y3a186mgq561mzw8h9f6jzs00f"))))
+    (build-system cargo-build-system)
+    (arguments
+     `(#:cargo-inputs
+       (("rust-ignore" ,rust-ignore-0.4)
+        ("rust-libtest-mimic" ,rust-libtest-mimic-0.6)
+        ("rust-toml-test" ,rust-toml-test-0.3)
+        ("rust-toml-test-data" ,rust-toml-test-data-1))))
+    (home-page "https://github.com/epage/toml-test-rs")
+    (synopsis "Cargo test harness for verifying TOML parsers")
+    (description "Cargo test harness for verifying TOML parsers.")
+    (license (list license:expat license:asl2.0))))
+
 (define-public rust-tonic-0.6
   (package
     (name "rust-tonic")