fix(tests): fix test isolation issues in terminal-multiplexer tests

- detection.test.ts: Save and restore env vars properly
- tmux-utils.test.ts: Delete env vars when originally undefined
- tmux-adapter.test.ts: Add cleanup to kill created tmux sessions

Fixes test isolation issues identified by cubic-dev-ai in PR code-yeongyu#1226.
Without these fixes, tests can be flaky when run inside tmux/zellij
and orphaned sessions accumulate.

Author: mrdavidlaing

src/shared/terminal-multiplexer/detection.test.ts

@@ -4,15 +4,38 @@ import { TmuxAdapter } from "./tmux-adapter"
 import { ZellijAdapter } from "./zellij-adapter"
 
 describe("detectMultiplexer", () => {
+  let savedTmux: string | undefined
+  let savedZellij: string | undefined
+  let savedZellijSession: string | undefined
+
   beforeEach(() => {
     resetDetectionCache()
+    savedTmux = process.env.TMUX
+    savedZellij = process.env.ZELLIJ
+    savedZellijSession = process.env.ZELLIJ_SESSION_NAME
     delete process.env.TMUX
     delete process.env.ZELLIJ
     delete process.env.ZELLIJ_SESSION_NAME
   })
 
   afterEach(() => {
     resetDetectionCache()
+    // Restore or delete based on original state
+    if (savedTmux !== undefined) {
+      process.env.TMUX = savedTmux
+    } else {
+      delete process.env.TMUX
+    }
+    if (savedZellij !== undefined) {
+      process.env.ZELLIJ = savedZellij
+    } else {
+      delete process.env.ZELLIJ
+    }
+    if (savedZellijSession !== undefined) {
+      process.env.ZELLIJ_SESSION_NAME = savedZellijSession
+    } else {
+      delete process.env.ZELLIJ_SESSION_NAME
+    }
   })
 
   it("returns 'tmux' when $TMUX env var is set", async () => {

src/shared/terminal-multiplexer/tmux-adapter.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect, beforeEach, mock } from "bun:test"
+import { describe, it, expect, beforeEach, afterEach, mock } from "bun:test"
 import { TmuxAdapter } from "./tmux-adapter"
 
 const mockConfig = {
@@ -148,9 +148,27 @@ describe("TmuxAdapter", () => {
   })
 
   describe("ensureSession", () => {
+    const createdSessions: string[] = []
+
+    beforeEach(() => {
+      createdSessions.length = 0
+    })
+
+    afterEach(async () => {
+      for (const sessionName of createdSessions) {
+        try {
+          await adapter.killSession(sessionName)
+        } catch {
+          // Ignore errors if session doesn't exist
+        }
+      }
+      createdSessions.length = 0
+    })
+
     it("accepts session name and creates session", async () => {
       //#given
       const sessionName = "omo-test-session"
+      createdSessions.push(sessionName)
 
       //#when
       const ensurePromise = adapter.ensureSession(sessionName)
@@ -162,6 +180,7 @@ describe("TmuxAdapter", () => {
     it("succeeds when session already exists", async () => {
       //#given
       const sessionName = "omo-existing-session"
+      createdSessions.push(sessionName)
       await adapter.ensureSession(sessionName)
 
       //#when
@@ -173,9 +192,27 @@ describe("TmuxAdapter", () => {
   })
 
   describe("killSession", () => {
+    const createdSessions: string[] = []
+
+    beforeEach(() => {
+      createdSessions.length = 0
+    })
+
+    afterEach(async () => {
+      for (const sessionName of createdSessions) {
+        try {
+          await adapter.killSession(sessionName)
+        } catch {
+          // Ignore errors if session doesn't exist
+        }
+      }
+      createdSessions.length = 0
+    })
+
     it("accepts session name and kills session", async () => {
       //#given
       const sessionName = "omo-kill-test"
+      createdSessions.push(sessionName)
       await adapter.ensureSession(sessionName)
 
       //#when

src/shared/tmux/tmux-utils.test.ts

@@ -24,9 +24,21 @@ describe("isInsideTmux", () => {
   })
 
   afterEach(() => {
-    process.env.TMUX = savedTmux
-    process.env.ZELLIJ = savedZellij
-    process.env.ZELLIJ_SESSION_NAME = savedZellijSession
+    if (savedTmux !== undefined) {
+      process.env.TMUX = savedTmux
+    } else {
+      delete process.env.TMUX
+    }
+    if (savedZellij !== undefined) {
+      process.env.ZELLIJ = savedZellij
+    } else {
+      delete process.env.ZELLIJ
+    }
+    if (savedZellijSession !== undefined) {
+      process.env.ZELLIJ_SESSION_NAME = savedZellijSession
+    } else {
+      delete process.env.ZELLIJ_SESSION_NAME
+    }
   })
 
   test("returns true when TMUX env is set", () => {