diff --git a/src/environment.ts b/src/environment.ts
index 6ea0e87e4..80759d6d6 100644
--- a/src/environment.ts
+++ b/src/environment.ts
@@ -193,10 +193,12 @@ export enum ActionsEnvVars {
   GITHUB_SERVER_URL = "GITHUB_SERVER_URL",
   GITHUB_SHA = "GITHUB_SHA",
   GITHUB_WORKFLOW = "GITHUB_WORKFLOW",
+  GITHUB_WORKSPACE = "GITHUB_WORKSPACE",
   RUNNER_ENVIRONMENT = "RUNNER_ENVIRONMENT",
   RUNNER_NAME = "RUNNER_NAME",
   RUNNER_OS = "RUNNER_OS",
   RUNNER_TEMP = "RUNNER_TEMP",
+  RUNNER_TOOL_CACHE = "RUNNER_TOOL_CACHE",
 }
 
 /** A type representing all known environment variables. */
diff --git a/src/testing-utils.ts b/src/testing-utils.ts
index 20cbadeab..fab26d57b 100644
--- a/src/testing-utils.ts
+++ b/src/testing-utils.ts
@@ -466,16 +466,18 @@ export function setupBaseActionsVars(
  * @param tempDir A value for `RUNNER_TEMP` and `GITHUB_WORKSPACE`.
  * @param toolsDir A value for `RUNNER_TOOL_CACHE`.
  * @param overrides Overrides for the defaults.
+ * @param env The environment to set the variables for.
  */
 export function setupActionsVars(
   tempDir: string,
   toolsDir: string,
   overrides?: ActionVarOverrides,
+  env: Env = getEnv(),
 ) {
-  setupBaseActionsVars(overrides);
-  process.env["RUNNER_TEMP"] = tempDir;
-  process.env["RUNNER_TOOL_CACHE"] = toolsDir;
-  process.env["GITHUB_WORKSPACE"] = tempDir;
+  setupBaseActionsVars(overrides, env);
+  env.set(ActionsEnvVars.RUNNER_TEMP, tempDir);
+  env.set(ActionsEnvVars.RUNNER_TOOL_CACHE, toolsDir);
+  env.set(ActionsEnvVars.GITHUB_WORKSPACE, tempDir);
 }
 
 type LogLevel = "debug" | "info" | "warning" | "error";