Dep injection

learn_go_with_tests/dependency_injection/README.md

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+# Dependency Injection
+
+https://quii.gitbook.io/learn-go-with-tests/go-fundamentals/dependency-injection
+

learn_go_with_tests/dependency_injection/go.mod

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+module dependency_injection
+
+go 1.21.0

learn_go_with_tests/dependency_injection/greet.go

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+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+)
+
+func Greet(writer io.Writer, name string) {
+	fmt.Fprintf(writer, "Hello, %s\n", name)
+}
+
+// func main() {
+// 	Greet(os.Stdout, "Drew")
+// }
+
+// Here you can see that since now our greeter function takes an object that
+// implements the io.Writer interface we can now pass an object like the http.ResponseWriter
+// to it.
+func MyGreeterHandler(w http.ResponseWriter, r *http.Request) {
+	Greet(w, "world")
+}
+
+func main() {
+	log.Fatal(http.ListenAndServe(":5001", http.HandlerFunc(MyGreeterHandler)))
+}

learn_go_with_tests/dependency_injection/greet_test.go

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+package main
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestGreet(t *testing.T) {
+	// The Buffer type from the bytes package implements the Writer interface, because it has the method Write(p []byte) (n int, err error)
+	buffer := bytes.Buffer{}
+	Greet(&buffer, "Chris")
+
+	got := buffer.String()
+	want := "Hello, Chris"
+
+	if got != want {
+		t.Errorf("got %q want %q", got, want)
+	}
+}