diff --git a/src/actions-util.ts b/src/actions-util.ts
index 592a70ace..dea22d5c5 100644
--- a/src/actions-util.ts
+++ b/src/actions-util.ts
@@ -21,6 +21,21 @@ import {
  */
 declare const __CODEQL_ACTION_VERSION__: string;
 
+/**
+ * Abstracts over GitHub Actions functions so that we do not have to stub
+ * global functions in tests.
+ */
+export interface ActionsEnv {
+  getOptionalInput: (name: string) => string | undefined;
+}
+
+/**
+ * Gets the real `ActionsEnv` used by production code.
+ */
+export function getActionsEnv(): ActionsEnv {
+  return { getOptionalInput };
+}
+
 /**
  * Wrapper around core.getInput for inputs that always have a value.
  * Also see getOptionalInput.
diff --git a/src/testing-utils.ts b/src/testing-utils.ts
index 1702d6835..2660c21a6 100644
--- a/src/testing-utils.ts
+++ b/src/testing-utils.ts
@@ -10,7 +10,7 @@ import test, {
 import nock from "nock";
 import * as sinon from "sinon";
 
-import { getActionVersion } from "./actions-util";
+import { ActionsEnv, getActionVersion } from "./actions-util";
 import { AnalysisKind } from "./analyses";
 import * as apiClient from "./api-client";
 import { GitHubApiDetails } from "./api-client";
@@ -172,6 +172,15 @@ export function makeMacro<Args extends unknown[]>(
   return wrapper;
 }
 
+/**
+ * Gets an `ActionsEnv` instance for use in tests.
+ */
+export function getTestActionsEnv(): ActionsEnv {
+  return {
+    getOptionalInput: () => undefined,
+  };
+}
+
 /**
  * Default values for environment variables typically set in an Actions
  * environment. Tests can override individual variables by passing them in the