Tests Coverage Tool

The Tests Coverage Tool is a comprehensive utility designed to measure code coverage for gRPC services based on their proto contracts. It provides detailed insights into various aspects of your service's coverage, helping you ensure that your tests thoroughly validate your gRPC endpoints. The tool gathers the following metrics:

• Total Coverage Percentage: The overall coverage percentage across all services;
• Service-Specific Coverage: The coverage percentage for each logical service within your gRPC API;
• Method Coverage: Whether each gRPC method is covered by tests (covered/not covered);
• Request/Response Coverage: Detailed coverage for each method, including the total request parameters, the number of covered parameters, and the coverage percentage;
• Parameter-Level Coverage: In-depth coverage details for each parameter within the request/response, allowing you to see which parts of your API are thoroughly tested;
• Deprecation Status: Information on whether methods and their parameters are deprecated, aiding in maintaining up-to-date and clean tests;
• Support for Multiple Services: The tool can handle coverage reporting for multiple gRPC services within a single project;
• Coverage history: The tool can maintain the history of overall service coverage, logical service coverage, and coverage of gRPC method request and response parameters.

You can see a report example here.

If you have any questions, you can ask @Nikita Filonov

Requires Go 1.27 or newer. Use the latest patch release of your Go version.

To add the library to your test project, run:

go get github.com/Nikita-Filonov/tests-coverage-tool@latest

Below is an example of how to set up the gRPC client with the coverage interceptor. Replace servicev1 with your generated protobuf package. TLS uses the system certificate pool; configure RootCAs for a private certificate authority.

package test

import (
	"context"
	"crypto/tls"
	"fmt"
	"testing"

	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"

	"github.com/Nikita-Filonov/tests-coverage-tool/tool/coverageinupt"
)

func TestGRPC(t *testing.T) {
	// Set up a gRPC client connection with the coverage interceptor
	conn, err := grpc.NewClient(
		"localhost:1000",
		grpc.WithTransportCredentials(credentials.NewTLS(&tls.Config{MinVersion: tls.VersionTLS12})),
		grpc.WithChainUnaryInterceptor(coverageinupt.CoverageInterceptor()),
	)
	if err != nil {
		t.Fatalf("Failed to create gRPC client: %v", err)
	}
	defer conn.Close()

	// Initialize the proto service client
	client := servicev1.NewServiceClient(conn)

	// Call a gRPC method; coverage data will be automatically saved in the specified directory
	resp, err := client.Get(context.Background(), &servicev1.GetRequest{})

	fmt.Println(resp, err)
}

Before generating the coverage report, ensure that the tests-coverage-tool is installed. This tool relies on server reflection to gather data, so your gRPC service must support server reflection; otherwise, the tool will be unable to measure service coverage.

To install the tool, run:

go install github.com/Nikita-Filonov/tests-coverage-tool/tests-coverage-tool@latest

Once installed, you can generate the coverage report with the following command:

tests-coverage-tool save-report

This will generate a coverage report based on the results gathered during your test runs.

The library includes a built-in function, report.ReadCoverageReportState, which simplifies reading the state from a JSON coverage report. This function serves as a helper for analytics and reporting purposes, allowing users to efficiently manage the output of a JSON coverage report

Here’s an example of how to use it:

package main

import (
	"fmt"
	"log"

	"github.com/Nikita-Filonov/tests-coverage-tool/tool/report"
)

func main() {
	// Read the coverage report state from the JSON file
	state, err := report.ReadCoverageReportState()
	if err != nil {
		log.Fatalf("Error reading coverage report state: %v\n", err)
	}

	// Perform actions with the coverage state
	fmt.Println(state)
}

In this example, the ReadCoverageReportState function reads the JSON coverage report, and you can then process the state variable for further analytics or reporting

The tool can be configured via environment variables or a YAML configuration file. YAML values override environment variables; unspecified YAML values retain the environment values or defaults. Below are the available options:

To save coverage history, you must retain the history file, which is configured using the environment variables TESTS_COVERAGE_HISTORY_DIR and TESTS_COVERAGE_HISTORY_FILE. By default, the history file will be stored in the root directory with the name coverage-history.json. You do not need to create this file manually—it will be automatically generated when you run the save-report command. After that, you simply need to keep the coverage-history.json file for subsequent report generations. Each time a new report is generated, the file will be automatically updated with the latest coverage history, and the history will be added to the coverage report.

If you wish to disable the coverage history functionality, you can set the TESTS_COVERAGE_HISTORY_DIR and TESTS_COVERAGE_HISTORY_FILE environment variables to empty strings. This can be done through the YAML configuration file using the historyDir and historyFile settings.

To save a coverage report, use the following command:

go run ./tests-coverage-tool save-report

This command will generate and save the coverage report based on the collected test data.

To initialize the pinned frontend version and copy its standalone HTML report, run:

git submodule update --init --recursive
go run ./tests-coverage-tool copy-report

The copied template is embedded in the backend binary. Update the submodule tag and commit in .gitmodules before copying a new frontend release.

To print the current configuration, use the following command:

go run ./tests-coverage-tool print-config

This command outputs the configuration settings currently in use, allowing you to verify and adjust as needed

Install Task, then clone the repository and install dependencies:

git clone https://github.com/Nikita-Filonov/tests-coverage-tool.git
cd tests-coverage-tool
go mod download
task install-tools

The embedded HTML template is included in the repository, so building and testing the backend does not require the frontend submodule. Initialize the submodule only when updating the report template with copy-report.

Run task or task --list to see all available tasks.

On systems without Task, run the equivalent Go commands directly:

go test -race -shuffle=on -count=1 -coverpkg './...' -covermode=atomic -coverprofile coverage.out ./...
go tool cover -func coverage.out
go build ./...

Coverage uses -coverpkg=./... to count calls from integration tests across all backend packages, including the CLI. Run go tool cover -html coverage.out to inspect coverage in your browser. This measures the tool's own Go code; the generated gRPC report measures coverage of service contracts.