Move slowTest into test/integration/index

Deduplicate slowTest into the shared integration test library.

test/integration/patch.js

@@ -5,18 +5,13 @@ const path = require("path");
 
 const factorio = require("lib/factorio");
 
+const { slowTest } = require("./index");
+
 
 // The server integration test is required to run before this one
 require("./server")
 
 describe("Integration of lib/factorio/patch", function() {
-	// Mark that this test depeneds on a test that takes a lot of time.
-	function slowTest(test) {
-		if (process.env.FAST_TEST) {
-			test.skip();
-		}
-	}
-
 	describe("patch()", function() {
 		let savePath = path.join("test", "temp", "integration", "saves", "test.zip");
 		it("should patch a freeplay game", async function() {