puppeteer/test/coverage-utils.js

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/**
* Copyright 2020 Google Inc. All rights reserved.
*
* 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
*
* http://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.
*/
/* We want to ensure that all of Puppeteer's public API is tested via our unit
* tests but we can't use a tool like Istanbul because the way it instruments code
* unfortunately breaks in Puppeteer where some of that code is then being executed in a browser context.
*
* So instead we maintain this coverage code which does the following:
* * takes every public method that we expect to be tested
* * replaces it with a method that calls the original but also updates a Map of calls
* * in an after() test callback it asserts that every public method was called.
*
* We run this when COVERAGE=1.
*/
const path = require('path');
const fs = require('fs');
/**
* @param {Map<string, boolean>} apiCoverage
* @param {Object} events
* @param {string} className
* @param {!Object} classType
*/
function traceAPICoverage(apiCoverage, events, className, classType) {
className = className.substring(0, 1).toLowerCase() + className.substring(1);
for (const methodName of Reflect.ownKeys(classType.prototype)) {
const method = Reflect.get(classType.prototype, methodName);
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if (
methodName === 'constructor' ||
typeof methodName !== 'string' ||
methodName.startsWith('_') ||
typeof method !== 'function'
)
continue;
apiCoverage.set(`${className}.${methodName}`, false);
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Reflect.set(classType.prototype, methodName, function (...args) {
apiCoverage.set(`${className}.${methodName}`, true);
return method.call(this, ...args);
});
}
if (events[classType.name]) {
for (const event of Object.values(events[classType.name])) {
if (typeof event !== 'symbol')
apiCoverage.set(`${className}.emit(${JSON.stringify(event)})`, false);
}
const method = Reflect.get(classType.prototype, 'emit');
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Reflect.set(classType.prototype, 'emit', function (event, ...args) {
if (typeof event !== 'symbol' && this.listenerCount(event))
apiCoverage.set(`${className}.emit(${JSON.stringify(event)})`, true);
return method.call(this, event, ...args);
});
}
}
const coverageLocation = path.join(__dirname, 'coverage.json');
const clearOldCoverage = () => {
try {
fs.unlinkSync(coverageLocation);
} catch (error) {
// do nothing, the file didn't exist
}
};
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const writeCoverage = (coverage) => {
fs.writeFileSync(coverageLocation, JSON.stringify([...coverage.entries()]));
};
const getCoverageResults = () => {
let contents;
try {
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contents = fs.readFileSync(coverageLocation, { encoding: 'utf8' });
} catch (error) {
console.error('Warning: coverage file does not exist or is not readable.');
}
const coverageMap = new Map(JSON.parse(contents));
return coverageMap;
};
const trackCoverage = () => {
clearOldCoverage();
const coverageMap = new Map();
before(() => {
const api = require('../lib/api');
const events = require('../lib/Events');
for (const [className, classType] of Object.entries(api))
traceAPICoverage(coverageMap, events, className, classType);
});
after(() => {
writeCoverage(coverageMap);
});
};
module.exports = {
trackCoverage,
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getCoverageResults,
};