I want to test function B
in the following codes to catch exception thrown from function A
with Mocha/Sinon
.
MyModule.js
(function(handler) {
// export methods
handler.B = B;
handler.A = A;
function A() {
// the third party API is called here
// some exception may be thrown from it
console.log('function A is invoked...');
}
function B() {
console.log('function B is invoked...');
try {
A();
} catch (err) {
console.log('Exception is ' + err);
}
}
})(module.exports);
However, it seems the function A
can NOT be mocked with following codes, as the original function A
still be called here.
var myModule = require('MyModule.js');
var _A;
it('should catach exception of function A', function(done) {
_A = sinon.stub(myModule, 'A', function() {
throw new Error('for test');
});
myModule.B();
_A.restore();
done();
});
Also it does not work in another way with stub
_A = sinon.stub(myModule, 'A');
_A.onCall(0).throws(new Error('for test'));
Could someone help me figure out what wrong with my codes?
The problem is that your reference to A
in the body of B
is referencing the original A
directly. If you instead reference this.A
, it should call the stub wrapped A
.
(function(handler) {
// export methods
handler.B = B;
handler.A = A;
function A() {
// the third party API is called here
// some exception may be thrown from it
console.log('function A is invoked...');
}
function B() {
console.log('function B is invoked...');
try {
// This is referencing `function A() {}`, change it to `this.A();`
A();
} catch (err) {
console.log('Exception is ' + err);
}
}
})(module.exports);
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