diff --git a/src/testSession.ts b/src/testSession.ts
index 73e67c1b..34653e4d 100644
--- a/src/testSession.ts
+++ b/src/testSession.ts
@@ -113,7 +113,7 @@ export class TestSession extends AsyncOptionalCreatable<TestSessionOptions> {
         projectDir = this.project.dir;
       }
 
-      // the default bin/run in execCmd will no longer resolve properly when
+      // The default bin/run in execCmd will no longer resolve properly when
       // a test project is used since process.cwd is changed.  If the
       // TESTKIT_EXECUTABLE_PATH env var is not being used, then set it
       // to use the bin/run from the cwd now.
@@ -265,10 +265,16 @@ export class TestSession extends AsyncOptionalCreatable<TestSessionOptions> {
             }
           }
 
-          // Add the json flag if it looks like an sfdx command so we can return
-          // parsed json in the command return.
-          if (cmd.split(' ')[0].includes('sfdx') && !cmd.includes('--json')) {
-            cmd += ' --json';
+          // Detect when running sfdx cli commands
+          if (cmd.split(' ')[0].includes('sfdx')) {
+            if (!shell.which('sfdx')) {
+              throw new Error('sfdx executable not found for running sfdx setup commands');
+            }
+            // Add the json flag if it looks like an sfdx command so we can return
+            // parsed json in the command return.
+            if (!cmd.includes('--json')) {
+              cmd += ' --json';
+            }
           }
 
           const rv = shell.exec(cmd, { silent: true });
diff --git a/test/unit/testProject.test.ts b/test/unit/testProject.test.ts
index a91345ad..57b6d854 100644
--- a/test/unit/testProject.test.ts
+++ b/test/unit/testProject.test.ts
@@ -92,6 +92,7 @@ describe('TestProject', () => {
   });
 
   it('should generate from a name', () => {
+    stubMethod(sandbox, shelljs, 'which').returns(true);
     const shellString = new ShellString('');
     shellString.code = 0;
     const execStub = stubMethod(sandbox, shelljs, 'exec').returns(shellString);
@@ -104,6 +105,7 @@ describe('TestProject', () => {
   });
 
   it('should generate by default', () => {
+    stubMethod(sandbox, shelljs, 'which').returns(true);
     const shellString = new ShellString('');
     shellString.code = 0;
     const execStub = stubMethod(sandbox, shelljs, 'exec').returns(shellString);
@@ -116,6 +118,7 @@ describe('TestProject', () => {
   });
 
   it('should error if project:create fails', () => {
+    stubMethod(sandbox, shelljs, 'which').returns(true);
     const shellString = new ShellString('');
     shellString.code = 1;
     shellString.stderr = 'project:create failed';
@@ -143,6 +146,7 @@ describe('TestProject', () => {
   });
 
   it('should zip project contents with defaults', async () => {
+    stubMethod(sandbox, shelljs, 'which').returns(true);
     const expectedRv = 'zip_test';
     const shellString = new ShellString('');
     shellString.code = 0;
@@ -161,6 +165,7 @@ describe('TestProject', () => {
   });
 
   it('should zip project contents with params', async () => {
+    stubMethod(sandbox, shelljs, 'which').returns(true);
     const expectedRv = 'zip_test';
     const shellString = new ShellString('');
     shellString.code = 0;
diff --git a/test/unit/testSession.test.ts b/test/unit/testSession.test.ts
index 072e0357..a144f1cb 100644
--- a/test/unit/testSession.test.ts
+++ b/test/unit/testSession.test.ts
@@ -148,6 +148,7 @@ describe('TestSession', () => {
     });
 
     it('should create a session with setup commands', async () => {
+      stubMethod(sandbox, shelljs, 'which').returns(true);
       const setupCommands = ['sfdx foo:bar -r testing'];
       const execRv = { result: { donuts: 'yum' } };
       const shellString = new ShellString(JSON.stringify(execRv));
@@ -170,6 +171,7 @@ describe('TestSession', () => {
     });
 
     it('should create a session with setup commands and retries', async () => {
+      stubMethod(sandbox, shelljs, 'which').returns(true);
       // set retry timeout to 0 ms so that the test runs quickly
       process.env.TESTKIT_SETUP_RETRIES_TIMEOUT = '0';
       const retries = 2;
@@ -198,6 +200,7 @@ describe('TestSession', () => {
     });
 
     it('should create a session with org creation setup commands', async () => {
+      stubMethod(sandbox, shelljs, 'which').returns(true);
       const setupCommands = ['sfdx org:create -f config/project-scratch-def.json'];
       const username = 'hey@ho.org';
       const execRv = { result: { username } };
@@ -224,6 +227,7 @@ describe('TestSession', () => {
     });
 
     it('should create a session without org creation if TESTKIT_ORG_USERNAME is defined', async () => {
+      stubMethod(sandbox, shelljs, 'which').returns(true);
       const overriddenUsername = 'sherpa@tyrolean.org';
       const homedir = path.join('some', 'other', 'home');
       stubMethod(sandbox, env, 'getString')
@@ -257,6 +261,7 @@ describe('TestSession', () => {
     });
 
     it('should error if setup command fails', async () => {
+      stubMethod(sandbox, shelljs, 'which').returns(true);
       const setupCommands = ['sfdx foo:bar -r testing'];
       const expectedCmd = `${setupCommands[0]} --json`;
       const execRv = 'Cannot foo before bar';
@@ -271,6 +276,22 @@ describe('TestSession', () => {
         expect((err as Error).message).to.equal(`Setup command ${expectedCmd} failed due to: ${shellString.stdout}`);
       }
     });
+
+    it('should error if sfdx not found to run setup commands', async () => {
+      stubMethod(sandbox, shelljs, 'which').returns(null);
+      const setupCommands = ['sfdx foo:bar -r testing'];
+      const execRv = 'Cannot foo before bar';
+      const shellString = new ShellString(JSON.stringify(execRv));
+      shellString.code = 1;
+      stubMethod(sandbox, shelljs, 'exec').returns(shellString);
+
+      try {
+        await TestSession.create({ setupCommands });
+        assert(false, 'TestSession.create() should throw');
+      } catch (err: unknown) {
+        expect((err as Error).message).to.equal('sfdx executable not found for running sfdx setup commands');
+      }
+    });
   });
 
   describe('clean', () => {