diff --git a/src/client/testing/testController/common/server.ts b/src/client/testing/testController/common/server.ts
index 661290bf49885..8797a861fb4aa 100644
--- a/src/client/testing/testController/common/server.ts
+++ b/src/client/testing/testController/common/server.ts
@@ -213,10 +213,10 @@ export class PythonTestServer implements ITestServer, Disposable {
                 // Take all output from the subprocess and add it to the test output channel. This will be the pytest output.
                 // Displays output to user and ensure the subprocess doesn't run into buffer overflow.
                 result?.proc?.stdout?.on('data', (data) => {
-                    spawnOptions?.outputChannel?.append(data);
+                    spawnOptions?.outputChannel?.append(data.toString());
                 });
                 result?.proc?.stderr?.on('data', (data) => {
-                    spawnOptions?.outputChannel?.append(data);
+                    spawnOptions?.outputChannel?.append(data.toString());
                 });
                 result?.proc?.on('exit', () => {
                     traceLog('Exec server closed.', uuid);
diff --git a/src/client/testing/testController/pytest/pytestDiscoveryAdapter.ts b/src/client/testing/testController/pytest/pytestDiscoveryAdapter.ts
index 44ab3746dde49..450e2ef1edf2e 100644
--- a/src/client/testing/testController/pytest/pytestDiscoveryAdapter.ts
+++ b/src/client/testing/testController/pytest/pytestDiscoveryAdapter.ts
@@ -89,10 +89,10 @@ export class PytestTestDiscoveryAdapter implements ITestDiscoveryAdapter {
         // Take all output from the subprocess and add it to the test output channel. This will be the pytest output.
         // Displays output to user and ensure the subprocess doesn't run into buffer overflow.
         result?.proc?.stdout?.on('data', (data) => {
-            spawnOptions.outputChannel?.append(data);
+            spawnOptions.outputChannel?.append(data.toString());
         });
         result?.proc?.stderr?.on('data', (data) => {
-            spawnOptions.outputChannel?.append(data);
+            spawnOptions.outputChannel?.append(data.toString());
         });
         result?.proc?.on('exit', () => {
             deferredExec.resolve({ stdout: '', stderr: '' });
diff --git a/src/client/testing/testController/pytest/pytestExecutionAdapter.ts b/src/client/testing/testController/pytest/pytestExecutionAdapter.ts
index 4a9a57b16fede..96d53db22c1c3 100644
--- a/src/client/testing/testController/pytest/pytestExecutionAdapter.ts
+++ b/src/client/testing/testController/pytest/pytestExecutionAdapter.ts
@@ -169,10 +169,10 @@ export class PytestTestExecutionAdapter implements ITestExecutionAdapter {
                 // Take all output from the subprocess and add it to the test output channel. This will be the pytest output.
                 // Displays output to user and ensure the subprocess doesn't run into buffer overflow.
                 result?.proc?.stdout?.on('data', (data) => {
-                    this.outputChannel?.append(data);
+                    this.outputChannel?.append(data.toString());
                 });
                 result?.proc?.stderr?.on('data', (data) => {
-                    this.outputChannel?.append(data);
+                    this.outputChannel?.append(data.toString());
                 });
 
                 result?.proc?.on('exit', () => {