ExiftoolContext

exiftool-contex is a context for zoroaster which allows to create ExiftoolProcess, open it, create temp jpeg and data file, and make sure they are removed, and exiftool is closed in the _destroy method. Full API description see below.

Install

npm i --save-dev exiftool-context

Publish

This package has to be published from a Linux, and not a Mac, because it contains a filename with unicode encoding, which will be published in a different form (see below)

How to use

Just specify ExiftoolContext as your test suite context.

const ExiftoolContext = require('exiftool-context')
 
const myModuleTestSuite = {
    context: ExiftoolContext,
    'should have correct metadata': (ctx) => {
        const ep = ctx.create()
        return ep.open().then(() => {
            // Context has a number of JPEG pictures with some metadata.
            return ep.readMetadata(ctx.jpegFile)
        })
        .then((res) => {
            const file = res.data[0]
            return ctx.assertJpegMetadata(file)
        })
    },
}
 
module.exports = myModuleTestSuite

zoroaster example/myModuleTestSuite

example
   myModuleTestSuite.js
    ✓  should have correct metadata
 
Executed 1 tests.

API

Fixtures are found in ./etc directory. These functions and properties are available:

jpegFile

CANON/IMG_9858.JPG

jpegFile2

CANON/IMG_9859.JPG

tempFile

You need to call ctx.createTempFile first, after which this will be set to a temp jpeg file, into which you can write some metadata.

dataFile

You need to call ctx.createDataFile first, after which this will be set to a data file which can be used to open exiftool with and write commands to.

defaultBin

Returns exiftool.

static replaceSlashes()

exiftool will print "File not found: test/fixtures/no_such_file.jpg" in case of error, even on windows. use this function to replace slashes on your platform.

fileDoesNotExist

no_such_file.jpg

fileDoesNotExist2

no_such_file2.jpg

folder

CANON

emptyFolder

empty

filenameWithEncoding

Return a fixture file with utf-encoded filename.

./etc/fixtures/Fọto.jpg

Here's some some additional info about Mac, git and unicode which can help in times of trouble.

Git and the Umlaut problem on Mac OS X

Encode to unicode

Filename that we test against is: \u0046\u1ECD\u0074\u006F\u002E\u006A\u0070\u0067

Fọto.jpg: F\u1ECDto.jpg (Yoruba language) (NFC)

Fọto.jpg: Fo\u0323to.jpg - apparently another way to represent it (NFD)

Although the actual file may be in the wanted form, if there are other files in the repo (probably preceding the test one) which are in another form, git will use their format for other files (a guess but when it was the case, the test was failing).

// snippet to check filenames in unicode
 
const basename = path.basename(ctx.filenameWithEncoding)
const dir = path.dirname(ctx.filenameWithEncoding)
 
console.log('File to read: %s', ctx.filenameWithEncoding)
console.log('Filename in unicode to read: %s', ctx.toUnicode(basename))
const res = fs.readdirSync(dir)
console.log('Files in fixtures:')
res.map(n => ` ${n}: ${ctx.toUnicode(n)}`).forEach(n => console.log(n))

assertJpegMetadata

A function which has hard-coded metadata in it to assert against fixtures metadata.

ep

An ExiftoolProcess instance. it is not set at first, call ctx.create() before accessing.

create(bin)

this._ep = new exiftool.ExiftoolProcess() // use dist-exiftool binary
this._ep = new exiftool.ExiftoolProcess(bin) // use specific binary
return this // allow chaining

Create a new instance with a given bin, and assign it to self.

open(options)

if (this.ep) {
    return this.ep.open(options)
}
throw new Error('ep has not been created')

Open exiftool.

createOpen(bin, options)

this.create(bin).open(options)

Create an instance and open it.

close()

this.ep.close()

Close instance

readMetadata()

ep.readMetadata()

Read metadata of a file

writeMetadata()

ep.writeMetadata()

Write metadata to a file

initAndReadMetadata()

ep.open.readMetadata()

Open ExiftoolProcess and read metadata

initAndWriteMetadata()

ep.open.writeMetadata()

Open ExiftoolProcess and write metadata

createTempFile()

Create a new temp file for testing. Currently clones a jpeg fixture.

createDataFile()

Create a data file which can be used to open exiftool

writeToDataFile(data)

Write some data to the data file.

destroy()

Perform the following:

• unlinkTempFile(this.dataFile)
• unlinkTempFile(this.tempFile)

That is, make sure that tests do not have open processes after them, or temp files.

toUnicode

Convert a string to unicode (author).

// http://buildingonmud.blogspot.ru/2009/06/convert-string-to-unicode-in-javascript.html
function toUnicode(theString) {
    let unicodeString = ''
    for (var i=0; i < theString.length; i++) {
        let theUnicode = theString.charCodeAt(i).toString(16).toUpperCase()
        while (theUnicode.length < 4) {
            theUnicode = '0' + theUnicode
        }
        theUnicode = '\\u' + theUnicode
        unicodeString += theUnicode
    }
    return unicodeString
}

MockSpawn

Because node-exiftool will be spawned with child_process.spawn, when testing, we will mock the spawn method. To do that, use ctx.mockSpawn(), and access the process's mock with ctx.proc. The process is an EventEmitter, and will emit close event when its stdin is written with -stay_open\nfalse\n.

ctx.mockSpawn()
const bin = 'echo'
const args = ['hello', 'world']
const options = {
    cwd: HOME,
}
const proc = cp.spawn(bin, args, options)
 
assert.equal(ctx.proc, proc)
assert.equal(ctx.proc.args, { bin, args, options })

When args passed to cp.spawn include -stay_open True, it will automatically push mocked date to the process's stderr, simulating an opening echo.

pushStderr(data: any)

Push some data to stderr readable stream.

pushStdout(data: any)

Push some data to stdout readable stream.

stdinData => {{chunk: Buffer, encoding: string}}[]

An array with all data written to stdin.

args => {{bin: string, args: string[], options: object}}

Arguments passed when calling child_process.spawn command.

What is a Test Context

A test context is an object which is available to tests via ctx argument. This is implemented in zoroaster test runner. It allows to abstract individual test contexts. That makes maintanence of test files easier when they don't have to rely on global scope of each other. You can create unique and specific tests contexts to be used in testing of your application. Save time by reusing the code, and using tests as a tool, and not the other way around.

To learn more about the idea of test contexts, read zoroaster documentation.

(c) Zoroaster 2017