[Improvement]: Test Double approach doesn't work as expected for function calls with path parameters

[DimuthuMadushan]

Description

Trying to create a test double for githubRestClient in this example. Since the example include the function call with path parameters(self.githubRestClient->/users/[owner]/repos;), I have used the following approach with appropriate return values.

final http:Client githubRestClient = check initRestClient();
function initRestClient() returns http:Client|error => check new ("https://api.github.com", {auth: {token: authToken}});

public client class MockHttpClient {

    remote function get(string path, map<string|string[]>? headers = (), http:TargetType targetType = http:Response) returns http:Response|anydata|http:ClientError {
    }

    resource function get [string... path](map<string|string[]>? headers = (), http:TargetType targetType = http:Response, *http:QueryParams params) returns http:Response|anydata {
    }

    remote function post (string path, http:RequestMessage message, map<string|string[]>? headers = (), string? mediaType = (), http:TargetType targetType = http:Response) returns http:Response|anydata|http:ClientError {
    }
}

@test:Mock {
    functionName: "initRestClient"
}
function initMockRestClient() returns http:Client|error {
    return test:mock(http:Client, new MockHttpClient());
}

When running the bal test command, it returns error: there are test failures.

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Describe your solution(s)

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Related area

-> Test Framework

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[Dilhasha]

Update:

• The initial issue in the above-defined test double was a return type mismatch. Identified an issue in the use of runtime generated main method for multi-module packages. Created an issue [Bug]: Runtime test exceptions are not thrown after using the generated main method for testable jar #40934

• Next, if we are expecting multiple responses for each path param we need to handle each case within the mock double. Check the following example.

public client class MockHttpClient {

    isolated resource function get [http:PathParamType... path](map<string|string[]>? headers = (), http:TargetType targetType = http:Response,
            *http:QueryParams params) returns http:Response|anydata|http:ClientError {
        GitHubRepository repo = {
            id: 1,
            name: "Test-Repo",
            'fork: false,
            created_at: "2020-10-10T10:10:10Z",
            updated_at: "2020-10-10T10:10:10Z",
            language: "Ballerina",
            has_issues: false,
            forks_count: 5,
            open_issues_count: 9,
            visibility: "Public",
            forks: 7,
            open_issues: 3,
            watchers: 55,
            default_branch: "master"
        };
        if path.toString().startsWith("/user") {
            GitHubUser user = {
                id: 1233,
                login: "balUser",
                url: "https://github.com/gitapi/users/balUser",
                created_at: "2020-10-10T10:10:10Z",
                updated_at: "2020-10-10T10:10:10Z",
                avatar_url: "https://avatars0.githubusercontent.com/u/1233?v=4",
                'type: "User",
                blog: "https://ballerina.io",
                company: "WSO2",
                name: "Ballerina User",
                location: "Sri Lanka"
            };
            return user;
        }
        if path.toString().startsWith("/users") && path.toString().endsWith("/repos") {
            return [repo];
        }
        if path.toString().startsWith("/repos") {
            if path.toString().endsWith("/issues") {
                Issue issue = {
                    number: 123
                };
                return issue;
            }
            return repo;
        }
        return error("error while mocking the response");
    }

    remote function post(string path, http:RequestMessage message, map<string|string[]>? headers = (), string? mediaType = (), http:TargetType targetType = http:Response)
            returns http:Response|anydata|http:ClientError {
        GitHubRepository expectedResult = {
            id: 1,
            name: "Test-Repo",
            'fork: false,
            created_at: "2020-10-10T10:10:10Z",
            updated_at: "2020-10-10T10:10:10Z",
            language: "Ballerina",
            has_issues: false,
            forks_count: 5,
            open_issues_count: 9,
            visibility: "Public",
            forks: 7,
            open_issues: 3,
            watchers: 55,
            default_branch: "master"
        };
        return expectedResult;
    }

}

[Dilhasha]

Based on above, it is error handling that is not working as expected and will be fixed with #40934