Detecting console.log() calls-Collection of common programming errors

You can replace console.log with your own function, which determines if it’s been called correctly. Here’s a example of how you could confirm that a function logs a certain message:

function doesLogMessage(f, message) {
    var oldLog = console.log,
        result = false;

    console.log = function(s) {
        if (s == message) {
            result = true;
        }
    };

    f();

    console.log = oldLog;

    return result;
}

Example Usage

function exampleFunction() {
    console.log("Hello World");
}

doesLogMessage(exampleFunction, "Hello World"); // true

function exampleFunction2() {
    console.log("Preparing world...");
    console.log("Hello World");
}

doesLogMessage(exampleFunction2, "Hello World"); // true

function exampleFunction3() { }

doesLogMessage(exampleFunction3, "Hello World"); // false

function exampleFunction4() {
    console.log("Goodbye World");
}

doesLogMessage(exampleFunction4, "Hello World"); // false