test-utilities: version test

Extract 'version test' to a reusable test utility as discussed in
https://github.com/NixOS/nixpkgs/pull/119636#issuecomment-826137021 and

pkgs/build-support/trivial-builders.nix

@@ -541,4 +541,37 @@ rec {
       phases = "unpackPhase patchPhase installPhase";
       installPhase = "cp -R ./ $out";
     };
+
+  /* Checks the command output contains the specified version
+   *
+   * Although simplistic, this test assures that the main program
+   * can run. While there's no substitute for a real test case,
+   * it does catch dynamic linking errors and such. It also provides
+   * some protection against accidentally building the wrong version,
+   * for example when using an 'old' hash in a fixed-output derivation.
+   *
+   * Examples:
+   *
+   * passthru.tests.version = testVersion { package = hello; };
+   *
+   * passthru.tests.version = testVersion {
+   *   package = seaweedfs;
+   *   command = "weed version";
+   * };
+   *
+   * passthru.tests.version = testVersion {
+   *   package = key;
+   *   command = "KeY --help";
+   *   # Wrong '2.5' version in the code. Drop on next version.
+   *   version = "2.5";
+   * };
+   */
+  testVersion =
+    { package,
+      command ? "${package.meta.mainProgram or package.pname or package.name} --version",
+      version ? package.version,
+    }: runCommand "test-version" { nativeBuildInputs = [ package ]; meta.timeout = 60; } ''
+      ${command} | grep -Fw ${version}
+      touch $out
+    '';
 }