Tests: Adds test to data-nimg data attribute based on layout prop.

[andersonleite]

Adds tests to the Image component to verify that the correct data is being exposed.
Based on #27899 and #28312

Bug

• Related issues linked using fixes #number
• Integration tests added
• Errors have helpful link attached, see contributing.md

Feature

• Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
• Related issues linked using fixes #number
• Integration tests added
• Documentation added
• Telemetry added. In case of a feature if it's used or not.
• Errors have helpful link attached, see contributing.md

Documentation / Examples

• Make sure the linting passes

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General

	vercel/next.js canary	andersonleite/next.js data-nimg-tests	Change
buildDuration	16.5s	16.3s	-129ms
buildDurationCached	3.7s	3.6s	-109ms
nodeModulesSize	61.7 MB	61.7 MB	✓

Page Load Tests Overall increase ✓

	vercel/next.js canary	andersonleite/next.js data-nimg-tests	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.083	2.949	-0.13
/ avg req/sec	810.79	847.67	+36.88
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.881	1.826	-0.05
/error-in-render avg req/sec	1329.18	1368.8	+39.62

Client Bundles (main, webpack, commons)

	vercel/next.js canary	andersonleite/next.js data-nimg-tests	Change
745.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.2 kB	42.2 kB	✓
main-HASH.js gzip	23.3 kB	23.3 kB	✓
webpack-HASH.js gzip	1.45 kB	1.45 kB	✓
Overall change	67.2 kB	67.2 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	andersonleite/next.js data-nimg-tests	Change
polyfills-a4..dd70.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	andersonleite/next.js data-nimg-tests	Change
_app-HASH.js gzip	979 B	979 B	✓
_error-HASH.js gzip	194 B	194 B	✓
amp-HASH.js gzip	312 B	312 B	✓
css-HASH.js gzip	329 B	329 B	✓
dynamic-HASH.js gzip	2.67 kB	2.67 kB	✓
head-HASH.js gzip	351 B	351 B	✓
hooks-HASH.js gzip	918 B	918 B	✓
image-HASH.js gzip	4.14 kB	4.14 kB	✓
index-HASH.js gzip	261 B	261 B	✓
link-HASH.js gzip	1.66 kB	1.66 kB	✓
routerDirect..HASH.js gzip	318 B	318 B	✓
script-HASH.js gzip	387 B	387 B	✓
withRouter-HASH.js gzip	320 B	320 B	✓
bb14e60e810b..30f.css gzip	125 B	125 B	✓
Overall change	13 kB	13 kB	✓

Client Build Manifests

	vercel/next.js canary	andersonleite/next.js data-nimg-tests	Change
_buildManifest.js gzip	491 B	491 B	✓
Overall change	491 B	491 B	✓

Rendered Page Sizes

	vercel/next.js canary	andersonleite/next.js data-nimg-tests	Change
index.html gzip	540 B	540 B	✓
link.html gzip	552 B	552 B	✓
withRouter.html gzip	534 B	534 B	✓
Overall change	1.63 kB	1.63 kB	✓

---

Webpack 4 Mode (Decrease detected ✓)

General

	vercel/next.js canary	andersonleite/next.js data-nimg-tests	Change
buildDuration	13.7s	13.4s	-284ms
buildDurationCached	5.7s	5.6s	-54ms
nodeModulesSize	61.7 MB	61.7 MB	✓

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	andersonleite/next.js data-nimg-tests	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.978	3.014	⚠️ +0.04
/ avg req/sec	839.63	829.54	⚠️ -10.09
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.822	1.849	⚠️ +0.03
/error-in-render avg req/sec	1372.42	1351.96	⚠️ -20.46

Client Bundles (main, webpack, commons)

	vercel/next.js canary	andersonleite/next.js data-nimg-tests	Change
16.HASH.js gzip	186 B	186 B	✓
677f882d2ed8..HASH.js gzip	14.1 kB	14.1 kB	✓
framework.HASH.js gzip	41.9 kB	41.9 kB	✓
main-HASH.js gzip	10.7 kB	10.7 kB	✓
webpack-HASH.js gzip	1.19 kB	1.19 kB	✓
Overall change	68.1 kB	68.1 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	andersonleite/next.js data-nimg-tests	Change
polyfills-a4..dd70.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	andersonleite/next.js data-nimg-tests	Change
_app-HASH.js gzip	964 B	964 B	✓
_error-HASH.js gzip	3.8 kB	3.8 kB	✓
amp-HASH.js gzip	552 B	552 B	✓
css-HASH.js gzip	333 B	333 B	✓
dynamic-HASH.js gzip	2.87 kB	2.87 kB	✓
head-HASH.js gzip	3.06 kB	3.06 kB	✓
hooks-HASH.js gzip	924 B	924 B	✓
index-HASH.js gzip	231 B	231 B	✓
link-HASH.js gzip	1.64 kB	1.64 kB	✓
routerDirect..HASH.js gzip	298 B	298 B	✓
script-HASH.js gzip	3.03 kB	3.03 kB	✓
withRouter-HASH.js gzip	295 B	295 B	✓
30809af5c834..565.css gzip	125 B	125 B	✓
Overall change	18.1 kB	18.1 kB	✓

Client Build Manifests

	vercel/next.js canary	andersonleite/next.js data-nimg-tests	Change
_buildManifest.js gzip	500 B	500 B	✓
Overall change	500 B	500 B	✓

Rendered Page Sizes

	vercel/next.js canary	andersonleite/next.js data-nimg-tests	Change
index.html gzip	585 B	585 B	✓
link.html gzip	597 B	597 B	✓
withRouter.html gzip	579 B	579 B	✓
Overall change	1.76 kB	1.76 kB	✓

Commit: 5483332

[styfle]

Thanks!