These steps cover writing and running your application:

1. From your Terminal or console application, create a new directory called ~/projects/go-programming-cookbook/chapter9/coverage, and navigate to this directory.
2. Run the following command:

$ go mod init github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter9/coverage

You should see a file called go.mod that contains the following:

module github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter9/coverage    

3. Create a file called coverage.go with the following content:

        package main

        import "errors"

        // Coverage is a simple function with some branching conditions
        func Coverage(condition bool) error {
            if condition {
                return errors.New("condition was set")
            }
            return nil
        }

4. Run the gotests -all -w command.
5. This will generate a file named coverage_test.go with the following content:

        package main

        import "testing"

        func TestCoverage(t *testing.T) {
            type args struct {
                condition bool
            }
            tests := []struct {
                name string
                args args
                wantErr bool
            }{
                // TODO: Add test cases.
            }
            for _, tt := range tests {
                t.Run(tt.name, func(t *testing.T) {
                    if err := Coverage(tt.args.condition); (err != nil) 
                    != tt.wantErr {
                        t.Errorf("Coverage() error = %v, wantErr %v", 
                        err, tt.wantErr)
                    }
                })
            }
        }

6. Fill in the TODO section with the following:

        {"no condition", args{true}, true},

7. Run the go test -cover command, and you will see the following output:

$ go test -cover 
PASS
coverage: 66.7% of statements
ok github.com/PacktPublishing/Go-Programming-Cookbook-Second-
Edition/chapter9/coverage 0.007s

8. Add the following item to the TODO section:

        {"condition", args{false}, false},

9. Run the go test -cover command, and you will see the following output:

$ go test -cover 
PASS
coverage: 100.0% of statements
ok github.com/PacktPublishing/Go-Programming-Cookbook-Second-
Edition/chapter9/coverage 0.007s

10. Run the following commands:

$ go test -coverprofile=cover.out 
$ go tool cover -html=cover.out -o coverage.html

11. Open the coverage.html file in a browser to see a graphical coverage report.
12. The go.mod file may be updated and the go.sum file should now be present in the top-level recipe directory.