Mock settings writes in ToolchainSelection tests (#1829)

The `should show open dialog for folder selection` test would write the
selected toolchain value into settings. This would break the integration
tests if you ran them after the unit tests because the location of
`swift` would be incorrect.

Author: plemarquand

test/unit-tests/ui/ToolchainSelection.test.ts

@@ -32,6 +32,7 @@ suite("ToolchainSelection Unit Test Suite", () => {
     const mockedVSCodeWindow = mockGlobalObject(vscode, "window");
     const mockedVSCodeCommands = mockGlobalObject(vscode, "commands");
     const mockedVSCodeEnv = mockGlobalObject(vscode, "env");
+    const mockedVSCodeWorkspace = mockGlobalObject(vscode, "workspace");
     let mockLogger: SwiftLogger;
 
     setup(() => {
@@ -57,6 +58,15 @@ suite("ToolchainSelection Unit Test Suite", () => {
         mockedVSCodeCommands.executeCommand.resolves(undefined);
         mockedVSCodeEnv.openExternal.resolves(true);
 
+        // Mock workspace configuration to prevent actual settings writes
+        const mockConfiguration = {
+            update: stub().resolves(),
+            inspect: stub().returns({}),
+            get: stub().returns(undefined),
+            has: stub().returns(false),
+        };
+        mockedVSCodeWorkspace.getConfiguration.returns(mockConfiguration);
+
         // Mock SwiftToolchain static methods
         stub(SwiftToolchain, "findXcodeInstalls").resolves([]);
         stub(SwiftToolchain, "getToolchainInstalls").resolves([]);