diff --git a/src/minitestTests.ts b/src/minitestTests.ts
index da92249..d071bef 100644
--- a/src/minitestTests.ts
+++ b/src/minitestTests.ts
@@ -30,7 +30,9 @@ export class MinitestTests extends Tests {
    * @return The raw output from the Minitest JSON formatter.
    */
   initTests = async () => new Promise<string>((resolve, reject) => {
-    let cmd = `${this.getTestCommand()} vscode:minitest:list`;
+    let cmd = this.withDefaultShell(
+      `${this.getTestCommand()} vscode:minitest:list`
+    );
 
     // Allow a buffer of 64MB.
     const execArgs: childProcess.ExecOptions = {
@@ -144,7 +146,9 @@ export class MinitestTests extends Tests {
       env: this.getProcessEnv()
     };
 
-    let testCommand = `${this.testCommandWithDebugger(debuggerConfig)} '${relativeLocation}:${line}'`;
+    let testCommand = this.withDefaultShell(
+      `${this.testCommandWithDebugger(debuggerConfig)} '${relativeLocation}:${line}'`
+    );
     this.log.info(`Running command: ${testCommand}`);
 
     let testProcess = childProcess.spawn(
@@ -172,7 +176,9 @@ export class MinitestTests extends Tests {
     };
 
     // Run tests for a given file at once with a single command.
-    let testCommand = `${this.testCommandWithDebugger(debuggerConfig)} '${relativeFile}'`;
+    let testCommand = this.withDefaultShell(
+      `${this.testCommandWithDebugger(debuggerConfig)} '${relativeFile}'`
+    );
     this.log.info(`Running command: ${testCommand}`);
 
     let testProcess = childProcess.spawn(
@@ -197,7 +203,9 @@ export class MinitestTests extends Tests {
       env: this.getProcessEnv()
     };
 
-    let testCommand = this.testCommandWithDebugger(debuggerConfig);
+    let testCommand = this.withDefaultShell(
+      this.testCommandWithDebugger(debuggerConfig)
+    );
     this.log.info(`Running command: ${testCommand}`);
 
     let testProcess = childProcess.spawn(
diff --git a/src/rspecTests.ts b/src/rspecTests.ts
index 12217ca..e168169 100644
--- a/src/rspecTests.ts
+++ b/src/rspecTests.ts
@@ -30,8 +30,13 @@ export class RspecTests extends Tests {
    * @return The raw output from the RSpec JSON formatter.
    */
   initTests = async () => new Promise<string>((resolve, reject) => {
-    let cmd = `${this.getTestCommandWithFilePattern()} --require ${this.getCustomFormatterLocation()}`
-              + ` --format CustomFormatter --order defined --dry-run`;
+    let cmd = this.withDefaultShell(
+      `${this.getTestCommandWithFilePattern()} \
+      --require ${this.getCustomFormatterLocation()} \
+      --format CustomFormatter \
+      --order defined \
+      --dry-run`
+    );
 
     this.log.info(`Running dry-run of RSpec test suite with the following command: ${cmd}`);
 
@@ -170,7 +175,9 @@ export class RspecTests extends Tests {
       env: this.getProcessEnv()
     };
 
-    let testCommand = `${this.testCommandWithFormatterAndDebugger(debuggerConfig)} '${testLocation}'`;
+    let testCommand = this.withDefaultShell(
+      `${this.testCommandWithFormatterAndDebugger(debuggerConfig)} '${testLocation}'`
+    );
     this.log.info(`Running command: ${testCommand}`);
 
     let testProcess = childProcess.spawn(
@@ -196,7 +203,9 @@ export class RspecTests extends Tests {
     };
 
     // Run tests for a given file at once with a single command.
-    let testCommand = `${this.testCommandWithFormatterAndDebugger(debuggerConfig)} '${testFile}'`;
+    let testCommand = this.withDefaultShell(
+      `${this.testCommandWithFormatterAndDebugger(debuggerConfig)} '${testFile}'`
+    );
     this.log.info(`Running command: ${testCommand}`);
 
     let testProcess = childProcess.spawn(
@@ -220,7 +229,9 @@ export class RspecTests extends Tests {
       shell: true
     };
 
-    let testCommand = this.testCommandWithFormatterAndDebugger(debuggerConfig);
+    let testCommand = this.withDefaultShell(
+      this.testCommandWithFormatterAndDebugger(debuggerConfig)
+    );
     this.log.info(`Running command: ${testCommand}`);
 
     let testProcess = childProcess.spawn(
diff --git a/src/tests.ts b/src/tests.ts
index ce29bd3..502fa56 100644
--- a/src/tests.ts
+++ b/src/tests.ts
@@ -13,6 +13,8 @@ export abstract class Tests {
   protected workspace: vscode.WorkspaceFolder;
   abstract testFrameworkName: string;
   protected debugCommandStartedResolver: Function | undefined;
+  // The path to the user's preferred command-line shell (like /bin/bash, /bin/zsh, etc.)
+  private readonly shell = process.env.SHELL?.replace(/(\s+)/g, "\\$1");
 
   /**
    * @param context Extension context provided by vscode.
@@ -519,6 +521,15 @@ export abstract class Tests {
     return this.context.asAbsolutePath('./ruby');
   }
 
+  /**
+   * Wrap a command in the user's default shell (if there is one).
+   *
+   * @return The wrapped command (or the original command if there is no default shell)
+   */
+  protected withDefaultShell = (command: string) => {
+    return this.shell ? `${this.shell} -ic "${command}"` : command;
+  }
+
   /**
    * Runs a single test.
    *