Fix echo signature and add tsd test

package.json

@@ -39,6 +39,7 @@
     "fmt:check": "prettier --check .",
     "build": "tsc",
     "test": "tsc && PATH=$(env -i bash -c 'echo $PATH') node_modules/.bin/uvu test -i fixtures",
+    "tsd": "tsd",
     "coverage": "c8 --check-coverage npm test -- -i package",
     "mutation": "stryker run"
   },
@@ -61,6 +62,7 @@
     "@stryker-mutator/core": "^6.0.2",
     "c8": "^7.11.3",
     "prettier": "^2.7.0",
+    "tsd": "^0.21.0",
     "typescript": "^4.8.0-dev.20220529",
     "uvu": "^0.5.3"
   },

src/goods.ts

@@ -29,7 +29,7 @@ export { default as os } from 'node:os'
 export let argv = minimist(process.argv.slice(2))
 export function updateArgv(params: { sliceAt: number }) {
   argv = minimist(process.argv.slice(params.sliceAt))
-  global.argv = argv
+  ;(global as any).argv = argv
 }
 
 export const globby = Object.assign(function globby(
@@ -52,7 +52,7 @@ export async function fetch(url: RequestInfo, init?: RequestInit) {
   return nodeFetch(url, init)
 }
 
-// A console.log() alternative which can take ProcessOutput.
+export function echo(...args: any[]): void
 export function echo(pieces: TemplateStringsArray, ...args: any[]) {
   let msg
   let lastIdx = pieces.length - 1

test-d/goods.test-d.ts

@@ -0,0 +1,22 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import { $ } from '../src/core.js'
+import { echo, sleep } from '../src/goods.js'
+
+echo`Date is ${await $`date`}`
+echo('Hello, world!')
+
+await sleep('1s')
+await sleep(1000)