diff --git a/src/commands/builtin_command_runner.ts b/src/commands/builtin_command_runner.ts
index 5ca69b6..10af44a 100644
--- a/src/commands/builtin_command_runner.ts
+++ b/src/commands/builtin_command_runner.ts
@@ -19,12 +19,23 @@ export class BuiltinCommandRunner implements ICommandRunner {
     if (args.length < 1) {
       // Do nothing.
       return;
+    } else if (args.length > 1) {
+      throw new Error("cd: too many arguments")
+    }
+    
+    let path = args[0]
+    if (path == "-") {
+      const oldPwd = context.environment.get("OLDPWD")
+      if (oldPwd === null) {
+        throw new Error("cd: OLDPWD not set")
+      }
+      path = oldPwd
     }
-    const path = args[0]  // Ignore other arguments?
-    // Need to handle path of "-". Maybe previous path is in an env var?  "OLDPWD"
 
     const { FS } = context.fileSystem
+    const oldPwd = FS.cwd()
     FS.chdir(path)
+    context.environment.set("OLDPWD", oldPwd)
     context.environment.set("PWD", FS.cwd())
   }
 }
diff --git a/tests/commands/cd.test.ts b/tests/commands/cd.test.ts
index 3899e07..f3e54b1 100644
--- a/tests/commands/cd.test.ts
+++ b/tests/commands/cd.test.ts
@@ -1,11 +1,55 @@
 import { shell_setup_simple } from "../shell_setup"
 
 describe("cd command", () => {
+  it("should do nothing if no arguments", async () => {
+    const { shell, output } = await shell_setup_simple()
+    await shell._runCommands("cd")
+    expect(output.text).toEqual("")
+  })
+
+  it("should error if more than one argument", async () => {
+    const { shell, output } = await shell_setup_simple()
+    await shell._runCommands("cd a b")
+    expect(output.text).toMatch(/cd: too many arguments/)
+  })
+
+  it("should change directory", async () => {
+    const { shell, output } = await shell_setup_simple()
+
+    await shell._runCommands("pwd")
+    expect(output.text).toEqual("/drive\r\n")
+    output.clear()
+
+    await shell._runCommands("cd dirA")
+    await shell._runCommands("pwd")
+    expect(output.text).toEqual("/drive/dirA\r\n")
+  })
+
   it("should update PWD", async () => {
     const { shell } = await shell_setup_simple()
     const { environment } = shell
+
     expect(environment.get("PWD")).toEqual("/drive")
     await shell._runCommands("cd dirA")
     expect(environment.get("PWD")).toEqual("/drive/dirA")
   })
+
+  it("should support cd -", async () => {
+    const { shell } = await shell_setup_simple()
+    const { environment } = shell
+
+    expect(environment.get("OLDPWD")).toBeNull()
+    await shell._runCommands("cd dirA")
+    expect(environment.get("PWD")).toEqual("/drive/dirA")
+    expect(environment.get("OLDPWD")).toEqual("/drive")
+    await shell._runCommands("cd -")
+    expect(environment.get("PWD")).toEqual("/drive")
+    expect(environment.get("OLDPWD")).toEqual("/drive/dirA")
+  })
+
+  it("should error if use cd - and OLDPWD not set", async () => {
+    const { shell, output } = await shell_setup_simple()
+    await shell._runCommands("cd -")
+    expect(output.text).toMatch(/cd: OLDPWD not set/)
+  })
 })