test: improve assertion messages

Print content of domain stack if it doesn't match expected values
PR-URL: https://github.com/nodejs/node/pull/16885
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>

test/parallel/test-domain-safe-exit.js

@@ -20,18 +20,21 @@
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 'use strict';
+require('../common');
 // Make sure the domain stack doesn't get clobbered by un-matched .exit()
 
-require('../common');
 const assert = require('assert');
 const domain = require('domain');
+const util = require('util');
 
 const a = domain.create();
 const b = domain.create();
 
 a.enter(); // push
 b.enter(); // push
-assert.deepStrictEqual(domain._stack, [a, b], 'b not pushed');
+assert.deepStrictEqual(domain._stack, [a, b], 'Unexpected stack shape ' +
+                       `(domain._stack = ${util.inspect(domain._stack)})`);
 
 domain.create().exit(); // no-op
-assert.deepStrictEqual(domain._stack, [a, b], 'stack mangled!');
+assert.deepStrictEqual(domain._stack, [a, b], 'Unexpected stack shape ' +
+                       `(domain._stack = ${util.inspect(domain._stack)})`);