test: use on-disk fixture for test-npm-install

Instead of writing the fixtures on the fly in the test,
put them in the fixtures directory that can be copied into
a temporary directory to reproduce in a debugger.

Signed-off-by: Joyee Cheung <joyeec9h3@gmail.com>

Author: joyeecheung

test/fixtures/npm-install/example/example.js

@@ -0,0 +1 @@
+exports.value = 42;

test/fixtures/npm-install/example/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "example",
+  "version": "1.0.0",
+  "main": "example.js"
+}

test/fixtures/npm-install/home/.gitkeep

@@ -0,0 +1,5 @@
+{
+  "dependencies": {
+    "example": "../example"
+  }
+}

test/fixtures/npm-install/install-dir/package.json

@@ -6,64 +6,37 @@ if (common.isInsideDirWithUnusualChars)
   common.skip('npm does not support this install path');
 
 const path = require('path');
-const exec = require('child_process').exec;
 const assert = require('assert');
 const fs = require('fs');
 const fixtures = require('../common/fixtures');
+const { spawnSyncAndAssert } = require('../common/child_process');
 
 const tmpdir = require('../common/tmpdir');
 tmpdir.refresh();
-const npmSandbox = tmpdir.resolve('npm-sandbox');
-fs.mkdirSync(npmSandbox);
-const homeDir = tmpdir.resolve('home');
-fs.mkdirSync(homeDir);
-const installDir = tmpdir.resolve('install-dir');
-fs.mkdirSync(installDir);
-
-const npmPath = path.join(
-  __dirname,
-  '..',
-  '..',
-  'deps',
-  'npm',
-  'bin',
-  'npm-cli.js'
-);
-
-const pkgContent = JSON.stringify({
-  dependencies: {
-    'package-name': fixtures.path('packages/main')
-  }
-});
 
-const pkgPath = path.join(installDir, 'package.json');
+// Copy fixtures/npm-install to the tmpdir for testing
+fs.cpSync(fixtures.path('npm-install'), tmpdir.path, { recursive: true });
 
-fs.writeFileSync(pkgPath, pkgContent);
+const npmPath = path.join(__dirname, '..', '..', 'deps', 'npm', 'bin', 'npm-cli.js');
 
-const env = { ...process.env,
-              PATH: path.dirname(process.execPath),
-              NODE: process.execPath,
-              NPM: npmPath,
-              NPM_CONFIG_PREFIX: path.join(npmSandbox, 'npm-prefix'),
-              NPM_CONFIG_TMP: path.join(npmSandbox, 'npm-tmp'),
-              NPM_CONFIG_AUDIT: false,
-              NPM_CONFIG_UPDATE_NOTIFIER: false,
-              HOME: homeDir };
+const env = {
+  ...process.env,
+  PATH: path.dirname(process.execPath),
+  NODE: process.execPath,
+  NPM: npmPath,
+  NPM_CONFIG_PREFIX: tmpdir.resolve('npm-prefix'),
+  NPM_CONFIG_TMP: tmpdir.resolve('npm-tmp'),
+  NPM_CONFIG_AUDIT: false,
+  NPM_CONFIG_UPDATE_NOTIFIER: false,
+  HOME: tmpdir.resolve('home'),
+};
 
-exec(`"${common.isWindows ? process.execPath : '$NODE'}" "${common.isWindows ? npmPath : '$NPM'}" install`, {
-  cwd: installDir,
-  env: env
-}, common.mustCall(handleExit));
-
-function handleExit(error, stdout, stderr) {
-  const code = error ? error.code : 0;
-  const signalCode = error ? error.signal : null;
-
-  if (code !== 0) {
-    process.stderr.write(stderr);
-  }
+const installDir = tmpdir.resolve('install-dir');
+spawnSyncAndAssert(
+  process.execPath,
+  [npmPath, 'install'],
+  { cwd: installDir, env },
+  {}
+);
 
-  assert.strictEqual(code, 0, `npm install got error code ${code}`);
-  assert.strictEqual(signalCode, null, `unexpected signal: ${signalCode}`);
-  assert(fs.existsSync(`${installDir}/node_modules/package-name`));
-}
+assert(fs.existsSync(path.join(installDir, 'node_modules', 'example')));