Karma Pipe Test: _this.handler.handle is not a function thrown - node.js

Question

I have two pipes in my Angular Projekt. The test for both of them look the same, and are just test for existance. One of them is failing with the error message: An error was thrown in afterAll\nUncaught TypeError: _this.handler.handle is not a function thrown
The test looks like the following:
it('create an instance', () => {
const pipe = new MyPipe();
expect(pipe).toBeTruthy();
});
Even when I change the code to not even creating the Pipe it still fails.
it('create an instance', () => {
expect(true).toBeTruthy();
});
So it seems to be something wrong with the test itself but I wasn't able to figure out why.
karma.conf.js
config.set({
basePath: '',
frameworks: ['jasmine', '#angular-devkit/build-angular'],
plugins: [
require('karma-jasmine'),
require('karma-chrome-launcher'),
require('karma-jasmine-html-reporter'),
require('karma-coverage-istanbul-reporter'),
require('#angular-devkit/build-angular/plugins/karma'),
require('karma-junit-reporter')
],
client: {
clearContext: false // leave Jasmine Spec Runner output visible in browser
},
coverageIstanbulReporter: {
dir: require('path').join(__dirname, 'coverage'),
reports: ['html', 'lcovonly', 'text-summary'],
fixWebpackSourcePaths: true
},
reporters: config.angularCli && config.angularCli.codeCoverage
? ['progress', 'coverage-istanbul', 'junit']
: ['progress', 'kjhtml', 'junit'],
junitReporter: {
outputFile: 'test-results.xml'
},
port: 9876,
colors: true,
logLevel: config.LOG_INFO,
autoWatch: true,
browsers: ['Chrome'],
singleRun: false
});

Answer 1

You should ensure the following is true in your code:
in the "spec" you are not including HttpClientModule and instead use HttpClientTestingModule
See the SO post here regarding that one:
TypeError: _this.handler.handle is not a function error
Also ensure that any subscribe from a http request has an error block.
Wrong:
this.myservice.func().subscribe(result => {
// do stuff
})
Right:
this.myservice.func().subscribe(result => {
// do stuff
}, error => {
// process error
})
See the SO post regarding that one:
Angular5 / ng test ERROR : TypeError: this.handler.handle is not a function
(top answer)
Note this is especially true if you do some sort of service call in ngInit.