diff --git a/dist/setup/index.js b/dist/setup/index.js
index 3d7a838e..855880b7 100644
--- a/dist/setup/index.js
+++ b/dist/setup/index.js
@@ -13926,8 +13926,8 @@ class MicrosoftDistributions extends base_installer_1.JavaBase {
             return jdkVersions;
         });
     }
-    getPlatformOption() {
-        switch (process.platform) {
+    getPlatformOption(platform = process.platform /* for testing */) {
+        switch (platform) {
             case 'darwin':
                 return { archive: 'tar.gz', os: 'macos' };
             case 'win32':
@@ -13935,7 +13935,7 @@ class MicrosoftDistributions extends base_installer_1.JavaBase {
             case 'linux':
                 return { archive: 'tar.gz', os: 'linux' };
             default:
-                throw new Error(`Platform '${process.platform}' is not supported. Supported platforms: 'darwin', 'linux', 'win32'`);
+                throw new Error(`Platform '${platform}' is not supported. Supported platforms: 'darwin', 'linux', 'win32'`);
         }
     }
     convertVersionToSemver(version) {
diff --git a/src/distributions/microsoft/installer.ts b/src/distributions/microsoft/installer.ts
index 5376cb29..79fffe5e 100644
--- a/src/distributions/microsoft/installer.ts
+++ b/src/distributions/microsoft/installer.ts
@@ -89,8 +89,10 @@ export class MicrosoftDistributions extends JavaBase {
     return jdkVersions;
   }
 
-  private getPlatformOption(): PlatformOptions {
-    switch (process.platform) {
+  private getPlatformOption(
+    platform: NodeJS.Platform = process.platform /* for testing */
+  ): PlatformOptions {
+    switch (platform) {
       case 'darwin':
         return { archive: 'tar.gz', os: 'macos' };
       case 'win32':
@@ -99,7 +101,7 @@ export class MicrosoftDistributions extends JavaBase {
         return { archive: 'tar.gz', os: 'linux' };
       default:
         throw new Error(
-          `Platform '${process.platform}' is not supported. Supported platforms: 'darwin', 'linux', 'win32'`
+          `Platform '${platform}' is not supported. Supported platforms: 'darwin', 'linux', 'win32'`
         );
     }
   }