In unit testing with Jasmine, the expected pattern of '^169.254$' did not match the actual pattern of /^169.254$/ as anticipated

I am new to Angular and have recently started working with the Karma and Jasmine test framework. However, after upgrading to angular 7, I encountered an error that was not present before.

[1A[2K[31mElectron 2.0.2 (Node 8.9.3) HostComponent should call ipAddressPattern and check IP bad IP FAILED[39m Expected '^169.254$' to be /^169.254$/. at at UserContext.it (karma-test-shim.js:298475:34418) at ZoneDelegate../node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke (karma-test-shim.js:295054:26) at ProxyZoneSpec../node_modules/zone.js/dist/proxy.js.ProxyZoneSpec.onInvoke (karma-test-shim.js:294539:39) at ZoneDelegate../node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke (karma-test-shim.js:295053:52) at Zone../node_modules/zone.js/dist/zone.js.Zone.run (karma-test-shim.js:294813:43) at runInTestZone (karma-test-shim.js:294104:34) at UserContext. (karma-test-shim.js:294119:20) at

Here is my code snippet for reference:

In unit test

it("should call ipAddressPattern and check IP bad IP", () => {
    expect(component.ipAddressPattern("169.254.11.11")).toBe(new RegExp(CommonConstants.BAD_IP_ADDRESS_PATTERN));
  });

The previous code used to be like this: 

expect(component.ipAddressPattern("169.254.11.11")).toBe(CommonConstants.BAD_IP_ADDRESS_PATTERN);
, which worked fine. However, after the upgrade, it resulted in a compilation issue. So, I made the necessary changes to fix it by using 
expect(component.ipAddressPattern("169.254.11.11")).toBe(new RegExp(CommonConstants.BAD_IP_ADDRESS_PATTERN))
. The definition of BAD_IP_ADDRESS_PATTERN in the common constant class is as follows:

public static readonly BAD_IP_ADDRESS_PATTERN: string = "^169\.254$";

Within other classes, the code looks like this:

public ipAddressPattern(ipAddress: string): RegExp {
    return CommonUtil.isBadIPAddress(ipAddress);
  }

The implementation within the CommonUtil class is shown below:

public static isBadIPAddress(ipAddress: string): any {
        if (ipAddress) {
            if (ipAddress.startsWith(CommonConstants.BAD_IP_ADDRESS)) {
                return CommonConstants.BAD_IP_ADDRESS_PATTERN;
            } else {
                return ValidationPatterns.IP_ADDRESS;
            }
        }
    }

I would greatly appreciate any suggestions on how to resolve this issue.

javascriptangulartypescriptunit-testingkarma-jasmine

Answer №1

In order to correct the issue, it is important to eliminate the usage of new RegExp(). This will prevent a new instance of RegExp from being created each time, which leads to test failure.

To address the compiling error, it is essential to adjust the return type of ipAddressPattern. Instead of returning a string, ensure that you are returning a RegExp object.

Therefore, the function signature should be: 

public ipAddressPattern(ipAddress: string): RegExp

Answer №2

When using javascript, it is important to note that the String.prototype.startsWith method (@line 3 in your CommonUtil class) requires a raw string as input, not a regular expression (in string format).

To properly test the 

component.ipAddressPattern("169.254.11.11")
function, make sure the expected result matches the RegExp found in 
CommonConstants.BAD_IP_ADDRESS_PATTERN
, removing any leading and trailing slashes.

Answer №3

After incorporating "@types/jasmine": "^2.8.7",, into the devDependencies section, the issue was resolved successfully. This is how I resolved it:

"devDependencies": {
    "@angular/compiler-cli": "^7.2.0",
    "@angular/language-service": "~7.2.0",
    "@types/jasminewd2": "~2.0.3",
    "@types/core-js": "^0.9.46",
    "@types/jasmine": "^2.8.7",
    ... other modules ...
}

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