diff --git a/test/cli/install/registry/bun-install-registry.test.ts b/test/cli/install/registry/bun-install-registry.test.ts
index 7bbe29152c..48952f9362 100644
--- a/test/cli/install/registry/bun-install-registry.test.ts
+++ b/test/cli/install/registry/bun-install-registry.test.ts
@@ -123,7 +123,9 @@ describe("optionalDependencies", () => {
         savesLockfile: !rootOptional,
       });
 
-      expect(err).toContain("warn: GET http://localhost:4873/this-package-does-not-exist-in-the-registry - ");
+      expect(err).toMatch(
+        `warn: GET http://localhost:${port}/this-package-does-not-exist-in-the-registry/-/this-package-does-not-exist-in-the-registry-1.0.0.tgz - `,
+      );
     });
   }
 });
@@ -455,7 +457,7 @@ registry = "http://localhost:${port}"
   const lockfile = await parseLockfile(packageDir);
   for (const pkg of Object.values(lockfile.packages) as any) {
     if (pkg.tag === "npm") {
-      expect(pkg.resolution.resolved).toContain("http://localhost:4873");
+      expect(pkg.resolution.resolved).toContain(`http://localhost:${port}`);
     }
   }
 
@@ -476,7 +478,7 @@ cache = "${cacheDir}"
   const npmLockfile = await parseLockfile(packageDir);
   for (const pkg of Object.values(npmLockfile.packages) as any) {
     if (pkg.tag === "npm") {
-      expect(pkg.resolution.resolved).not.toContain("http://localhost:4873");
+      expect(pkg.resolution.resolved).not.toContain(`http://localhost:${port}`);
     }
   }
 });
diff --git a/test/harness.ts b/test/harness.ts
index ab539d183b..f470711bd2 100644
--- a/test/harness.ts
+++ b/test/harness.ts
@@ -57,30 +57,8 @@ export function nodeExe(): string | null {
   return which("node") || null;
 }
 
-export function bashExe(): string {
-  const bash = which("bash");
-  if (!bash) {
-    throw new Error("Failed to find 'bash'");
-  }
-  return bash;
-}
-
-export function pwshExe(): string {
-  if (!isWindows) {
-    throw new Error("Powershell is only supported on Windows");
-  }
-  const pwsh = which("pwsh") || which("powershell");
-  if (!pwsh) {
-    throw new Error("Failed to find 'pwsh' or 'powershell'");
-  }
-  return pwsh;
-}
-
 export function shellExe(): string {
-  if (isWindows) {
-    return bashExe() || pwshExe();
-  }
-  return bashExe();
+  return isWindows ? "pwsh" : "bash";
 }
 
 export function gc(force = true) {
diff --git a/test/js/bun/test/expect.test.js b/test/js/bun/test/expect.test.js
index e1161ff7ed..692e5d2ee8 100644
--- a/test/js/bun/test/expect.test.js
+++ b/test/js/bun/test/expect.test.js
@@ -2231,12 +2231,19 @@ describe("expect()", () => {
       expect(thisFile).toHaveLength(thisFileSize);
       expect(thisFile).toHaveLength(Bun.file(__filename).size);
 
+      const { join } = require("path");
+      const { tmpdir } = require("os");
+      const { mkdtempSync, writeFileSync } = require("fs");
+      const tmpDir = mkdtempSync(join(tmpdir(), "jest-extended-"));
+      const tmpFile = join(tmpDir, "empty.txt");
+      writeFileSync(tmpFile, "");
+
       // empty file should have length 0
-      require("fs").writeFileSync("/tmp/empty.txt", "");
       expect(Bun.file("/tmp/empty.txt")).toHaveLength(0);
 
       // if a file doesn't exist, it should throw (not return 0 size)
-      expect(() => expect(Bun.file("/does-not-exist/file.txt")).toHaveLength(0)).toThrow();
+      const emptyFile = join(tmpDir, "does-not-exist.txt");
+      expect(() => expect(Bun.file(emptyFile)).toHaveLength(0)).toThrow();
 
       // Blob
       expect(new Blob(ANY([1, 2, 3]))).toHaveLength(3);
diff --git a/test/js/bun/test/jest-extended.test.js b/test/js/bun/test/jest-extended.test.js
index 0cc9c42aac..be0b6465d7 100644
--- a/test/js/bun/test/jest-extended.test.js
+++ b/test/js/bun/test/jest-extended.test.js
@@ -45,18 +45,22 @@ describe("jest-extended", () => {
       new Uint8Array(),
       new Object(),
       Buffer.from(""),
-      ...(isBun ? [Bun.file("/tmp/empty.txt")] : []),
       new Headers(),
       new URLSearchParams(),
       new FormData(),
       (function* () {})(),
     ];
+    if (isBun) {
+      const { join } = require("path");
+      const { tmpdir } = require("os");
+      const { mkdtempSync, writeFileSync } = require("fs");
+      const tmpDir = mkdtempSync(join(tmpdir(), "jest-extended-"));
+      const tmpFile = join(tmpDir, "empty.txt");
+      values.push(Bun.file(tmpFile));
+      writeFileSync(tmpFile, "");
+    }
     for (const value of values) {
       test(label(value), () => {
-        if (value && typeof value === "object" && value instanceof Blob) {
-          require("fs").writeFileSync("/tmp/empty.txt", "");
-        }
-
         expect(value).toBeEmpty();
       });
     }
diff --git a/test/js/third_party/st.test.ts b/test/js/third_party/st.test.ts
index 418a126c74..5ea9a11d89 100644
--- a/test/js/third_party/st.test.ts
+++ b/test/js/third_party/st.test.ts
@@ -1,22 +1,22 @@
-import { bunExe } from "bun:harness";
-import { bunEnv } from "harness";
+import { bunExe, bunEnv } from "harness";
 import { expect, it } from "bun:test";
-import * as path from "node:path";
+import { join, dirname } from "node:path";
 
 it("works", async () => {
-  const fixture_path = path.join(import.meta.dirname, "_fixtures", "st.ts");
+  const fixture_path = join(import.meta.dirname, "_fixtures", "st.ts");
   const fixture_data = await Bun.file(fixture_path).text();
   let { stdout, stderr, exited } = Bun.spawn({
     cmd: [bunExe(), "run", fixture_path],
-    cwd: path.dirname(fixture_path),
+    cwd: dirname(fixture_path),
     stdout: "pipe",
     stdin: "ignore",
     stderr: "pipe",
     env: bunEnv,
   });
-  // err = await new Response(stderr).text();
-  // expect(err).toBeEmpty();
-  let out = await new Response(stdout).text();
+  let [code, err, out] = await Promise.all([exited, new Response(stderr).text(), new Response(stdout).text()]);
+  if (code !== 0) {
+    expect(err).toBeEmpty();
+  }
   expect(out).toEqual(fixture_data + "\n");
-  expect(await exited).toBe(0);
+  expect(code).toBe(0);
 });