gnu: Add rust-tower-test-0.3.

* gnu/packages/crates-io.scm (rust-tower-test-0.3): New variable.

gnu/packages/crates-io.scm

@@ -27931,6 +27931,35 @@ composition between @code{Service}s.")
 request/response based, client or server.")
     (license license:expat)))
 
+(define-public rust-tower-test-0.3
+  (package
+    (name "rust-tower-test")
+    (version "0.3.0")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (crate-uri "tower-test" version))
+       (file-name (string-append name "-" version ".tar.gz"))
+       (sha256
+        (base32
+         "1j2k07g3z8ascq7r30bmw3b75v8lhd63mhfl60y59a74q71bp94v"))))
+    (build-system cargo-build-system)
+    (arguments
+     `(#:cargo-inputs
+       (("rust-futures-util" ,rust-futures-util-0.3)
+        ("rust-pin-project" ,rust-pin-project-0.4)
+        ("rust-tokio" ,rust-tokio-0.2)
+        ("rust-tokio-test" ,rust-tokio-test-0.2)
+        ("rust-tower-layer" ,rust-tower-layer-0.3)
+        ("rust-tower-service" ,rust-tower-service-0.3))
+       #:cargo-development-inputs
+       (("rust-tokio" ,rust-tokio-0.2))))
+    (home-page "https://github.com/tower-rs/tower")
+    (synopsis "Utilities for writing client and server @code{Service} tests")
+    (description "This package provides utilities for writing client and
+server @code{Service} tests.")
+    (license license:expat)))
+
     (description
      "This package provides a native Rust encoder and decoder of TOML-formatted
 files and streams.  Provides implementations of the standard