Mock TanzuHub Server for Writing Unit Tests

This package allows plugin authors to easily write unit tests using a mock GraphQL server endpoint for plugins that interact with the Tanzu Hub endpoint.

Note: This feature is EXPERIMENTAL. The API signature and implementation are subject to change or removal if an alternative means of providing equivalent functionality is introduced.

Using the Mock Server to Write Unit Tests

To mock a response for GraphQL queries, plugin authors can follow these simple steps:

1. Start the mock server:

import hubtesting "github.com/vmware-tanzu/tanzu-plugin-runtime/client/hub/testing"

hubMockServer := hubtesting.NewServer(t, WithQuery(...))
defer hubMockServer.Close()

1. Create a mockHubClient with the newly started server:

import "github.com/vmware-tanzu/tanzu-plugin-runtime/client/hub"

mockHubClient, err = hub.NewClient(c.CurrentContext, hub.WithEndpoint(hubMockServer.URL), hub.WithAccessToken("fake-token"))

1. To reuse a server across multiple unit tests, use hubMockServer.Reset() to clean up any previously registered queries, mutations, or errors.

2. To register mock queries or mutations, use the hubMockServer.RegisterQuery or hubMockServer.RegisterMutation APIs, which accept Operation objects.

Defining an Operation Object to Mock a Response

Let's assume your GraphQL query looks like the following:

query QueryAllProjects {
  applicationEngineQuery {
    queryProjects(first: 1000) {
      projects {
        json
      }
    }
  }
}

The following Operation type defines what values should be provided to the object:

// Operation is a general type that encompasses the Operation type and Response which
// is of the same type, but with data.
type Operation struct {
    // opType denotes whether the operation is a query or a mutation, using the opQuery
    // and opMutation constants. This is unexported as it is set by the *Server.RegisterQuery
    // and *Server.RegisterMutation functions, respectively.
    opType int

    // Identifier helps identify the operation in a request when coming through the Server.
    // For example, if your operation looks like this:
    //
    //   query {
    //     myOperation(foo: $foo) {
    //       fieldOne
    //        fieldTwo
    //     }
    //  }
    //
    // Then this field should be set to myOperation. It can also be more specific, a simple
    // strings.Contains check occurs to match operations. A more specific example of a
    // valid Identifier for the same operation given above would be myOperation(foo: $foo).
    Identifier string

    // Variables represents the map of variables that should be passed along with the
    // operation whenever it is invoked on the Server.
    Variables map[string]interface{}

    // Response represents the response that should be returned whenever the server makes
    // a match on Operation.opType, Operation.Name, and Operation.Variables.
    Response interface{}
}

If you have already generated the Go stubs using make tanzu-hub-stub-generate, all the Go type definitions necessary for writing the sample response should be available to you. These definitions might look like this based on the defined schema:

// QueryAllProjectsApplicationEngineQuery includes the requested fields of the GraphQL type ApplicationEngineQuery.
type QueryAllProjectsApplicationEngineQuery struct {
    QueryProjects QueryAllProjectsApplicationEngineQueryQueryProjectsKubernetesKindProjectConnection `json:"queryProjects"`
}

// QueryAllProjectsApplicationEngineQueryQueryProjectsKubernetesKindProjectConnection includes the requested fields of the GraphQL type KubernetesKindProjectConnection.
type QueryAllProjectsApplicationEngineQueryQueryProjectsKubernetesKindProjectConnection struct {
    Projects []QueryAllProjectsApplicationEngineQueryQueryProjectsKubernetesKindProjectConnectionProjectsKubernetesKindProject `json:"projects"`
}

// QueryAllProjectsApplicationEngineQueryQueryProjectsKubernetesKindProjectConnectionProjectsKubernetesKindProject includes the requested fields of the GraphQL type KubernetesKindProject.
type QueryAllProjectsApplicationEngineQueryQueryProjectsKubernetesKindProjectConnectionProjectsKubernetesKindProject struct {
    // Raw JSON response as produced by KRM API
    Json json.RawMessage `json:"json"`
}

To create a testing.Operation object, we will reuse these generated type definitions to create a mock response object:

import hubtesting "github.com/vmware-tanzu/tanzu-plugin-runtime/client/hub/testing"

type QueryResponse struct {
    ApplicationEngineQuery hub.QueryAllProjectsApplicationEngineQuery
}

mockResponse := hubtesting.Operation{
    Identifier: "QueryAllProjects",
    Response: QueryResponse{
        hub.QueryAllProjectsApplicationEngineQuery{
            QueryProjects: hub.QueryAllProjectsApplicationEngineQueryQueryProjectsKubernetesKindProjectConnection{
                Projects: []hub.QueryAllProjectsApplicationEngineQueryQueryProjectsKubernetesKindProjectConnectionProjectsKubernetesKindProject{
                    {
                        Json: jsonBytesForProject1,
                    },
                    {
                        Json: jsonBytesForProject2,
                    },
                },
            },
        },
    },
}

hubMockServer.RegisterQuery(mockResponse)