How to do it...

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/tools, and navigate to this directory.

2. Run the following command:

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

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

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

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

        package tools

        import (
            "fmt"
        )

        func example() error {
            fmt.Println("in example")
            return nil
        }

        var example2 = func() int {
            fmt.Println("in example2")
            return 10
        }

4. Create a file called structs.go with the following content:

        package tools

        import (
            "errors"
            "fmt"
        )

        type c struct {
            Branch bool
        }

        func (c *c) example3() error {
            fmt.Println("in example3")
            if c.Branch {
                fmt.Println("branching code!")
                return errors.New("bad branch")
            }

            return nil
        }

5. Create a file called funcs_test.go with the following content:

        package tools

        import (
            "testing"

            . "github.com/smartystreets/goconvey/convey"
        )

        func Test_example(t *testing.T) {
            tests := []struct {
                name string
            }{
                {"base-case"},
            }
            for _, tt := range tests {
                Convey(tt.name, t, func() {
                    res := example()
                    So(res, ShouldBeNil)
                })
            }
        }

        func Test_example2(t *testing.T) {
            tests := []struct {
                name string
            }{
                {"base-case"},
            }
            for _, tt := range tests {
                Convey(tt.name, t, func() {
                    res := example2()
                    So(res, ShouldBeGreaterThanOrEqualTo, 1)
                })
            }
        }

6. Create a file called structs_test.go with the following content:

        package tools

        import (
            "testing"

            . "github.com/smartystreets/goconvey/convey"
        )

        func Test_c_example3(t *testing.T) {
            type fields struct {
                Branch bool
            }
            tests := []struct {
                name string
                fields fields
                wantErr bool
            }{
                {"no branch", fields{false}, false},
                {"branch", fields{true}, true},
            }
            for _, tt := range tests {
                Convey(tt.name, t, func() {
                    c := &c{
                        Branch: tt.fields.Branch,
                    }
                    So((c.example3() != nil), ShouldEqual, tt.wantErr)
                })
            }
        }

7. Run the gocov test | gocov report command, and you will see the following output:

$ gocov test | gocov report
ok github.com/PacktPublishing/Go-Programming-Cookbook-Second-
Edition/chapter9/tools 0.006s 
coverage: 100.0% of statements

github.com/PacktPublishing/Go-Programming-Cookbook-Second-
Edition/chapter9/tools/struct.go 
c.example3 100.00% (5/5)
github.com/PacktPublishing/Go-Programming-Cookbook-Second-
Edition/chapter9/tools/funcs.go example 
100.00% (2/2)
github.com/PacktPublishing/Go-Programming-Cookbook-Second-
Edition/chapter9/tools/funcs.go @12:16 
100.00% (2/2)
github.com/PacktPublishing/Go-Programming-Cookbook-Second-
Edition/chapter9/tools ---------- 
100.00% (9/9)

Total Coverage: 100.00% (9/9)

8. Run the goconvey command, and it will open a browser that should look like this:

9. Ensure that all the tests pass.
10. The go.mod file may be updated and the go.sum file should now be present in the top-level recipe directory.