make the root tap object a true global singleton

fix: #1005

src/core/src/tap.ts

@@ -25,7 +25,7 @@ import { TestBase } from './test-base.js'
 
 const stdout = proc?.stdout
 
-const privSym = Symbol('private constructor')
+const privSym = Symbol.for('TAP private constructor')
 type PrivateTAPCtor = {
   [privSym]: true
 }
@@ -122,7 +122,7 @@ class TAP extends Test {
     // plugins get applied right here:
     super(options)
 
-    instance = this
+    instance = g[privSym] = this
     this.on('idle', () => maybeAutoend())
     this.on('complete', (results: FinalResults) =>
       this.#oncomplete(results)
@@ -483,6 +483,10 @@ const ignoreEPIPE = () => {
   }
 }
 
+const g = globalThis as typeof globalThis & {
+  [privSym]: TAP
+}
+
 /**
  * The exported function instantiates a {@link @tapjs/core!tap.TAP} object if
  * we don't already have one, or return the one that was previously
@@ -492,5 +496,6 @@ const ignoreEPIPE = () => {
  * but they are ignored if the instance was already created.
  */
 export const tap = (opts?: TestOpts) =>
-  instance || new TAP(privateTAPCtor, opts)
+  instance ?? g[privSym] ?? new TAP(privateTAPCtor, opts)
+
 export type { TAP }

src/core/test/tap.ts

@@ -4,6 +4,9 @@ import stripAnsi from 'strip-ansi-cjs'
 import { fileURLToPath } from 'url'
 import { env } from '../dist/esm/proc.js'
 import { tap } from '../dist/esm/tap.js'
+import { createRequire } from 'node:module'
+const req = createRequire(import.meta.url)
+const { tap: cjsTap } = req('../dist/commonjs/tap.js')
 
 const __filename = fileURLToPath(import.meta.url)
 
@@ -23,6 +26,7 @@ type Result = {
 const main = () => {
   const t = tap({ some: 'options' })
   t.equal(t.options.some, 'options')
+  t.equal(t, cjsTap())
   const clean = (s: string) =>
     stripAnsi(s)
       .replace(/# time=[0-9.]+m?s\n/g, '# time={TIME}\n')