diff --git a/scripts/postcss/tests/common.js b/scripts/postcss/tests/common.js
new file mode 100644
index 00000000..78ae847e
--- /dev/null
+++ b/scripts/postcss/tests/common.js
@@ -0,0 +1,30 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+const postcss = require("postcss");
+
+module.exports.createTestRunner = function (plugin) {
+    return async function run(input, output, opts = {}, assert) {
+        let result = await postcss([plugin(opts)]).process(input, { from: undefined, });
+        assert.strictEqual(
+            result.css.replaceAll(/\s/g, ""),
+            output.replaceAll(/\s/g, "")
+        );
+        assert.strictEqual(result.warnings().length, 0);
+    };
+}
+
+
diff --git a/scripts/postcss/tests/css-compile-variables.test.js b/scripts/postcss/tests/css-compile-variables.test.js
index 945d5d4d..e20e195f 100644
--- a/scripts/postcss/tests/css-compile-variables.test.js
+++ b/scripts/postcss/tests/css-compile-variables.test.js
@@ -18,15 +18,7 @@ const offColor = require("off-color").offColor;
 const postcss = require("postcss");
 const plugin = require("../css-compile-variables");
 const derive = require("../color").derive;
-
-async function run(input, output, opts = {}, assert) {
-    let result = await postcss([plugin({ ...opts, derive })]).process(input, { from: undefined, });
-    assert.strictEqual(
-        result.css.replaceAll(/\s/g, ""),
-        output.replaceAll(/\s/g, "")
-    );
-    assert.strictEqual(result.warnings().length, 0);
-}
+const run = require("./common").createTestRunner(plugin);
 
 module.exports.tests = function tests() {
     return {
@@ -46,7 +38,7 @@ module.exports.tests = function tests() {
                 --foo-color--lighter-50: ${transformedColor.hex()};
             }
             `;
-            await run( inputCSS, outputCSS, {}, assert);
+            await run( inputCSS, outputCSS, {derive}, assert);
         },
 
         "derived variables work with alias": async (assert) => {
@@ -66,7 +58,7 @@ module.exports.tests = function tests() {
                 --my-alias--lighter-15: ${aliasLighter};
             }
             `;
-            await run(inputCSS, outputCSS, { }, assert);
+            await run(inputCSS, outputCSS, {derive}, assert);
         },
 
         "derived variable throws if base not present in config": async (assert) => {
@@ -94,7 +86,7 @@ module.exports.tests = function tests() {
                 --foo-color--darker-20: ${transformedColor2.hex()};
             }
             `;
-            await run( inputCSS, outputCSS, { }, assert);
+            await run( inputCSS, outputCSS, {derive}, assert);
         },
 
         "multiple aliased-derived variable in single declaration is parsed correctly": async (assert) => {
diff --git a/scripts/postcss/tests/css-url-to-variables.test.js b/scripts/postcss/tests/css-url-to-variables.test.js
index 645b1775..0369995b 100644
--- a/scripts/postcss/tests/css-url-to-variables.test.js
+++ b/scripts/postcss/tests/css-url-to-variables.test.js
@@ -14,17 +14,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-const postcss = require("postcss");
 const plugin = require("../css-url-to-variables");
-
-async function run(input, output, opts = {}, assert) {
-    let result = await postcss([plugin(opts)]).process(input, { from: undefined, });
-    assert.strictEqual(
-        result.css.replaceAll(/\s/g, ""),
-        output.replaceAll(/\s/g, "")
-    );
-    assert.strictEqual(result.warnings().length, 0);
-}
+const run = require("./common").createTestRunner(plugin);
 
 module.exports.tests = function tests() {
     return {