feat: add greet program and tests

.gitignore

@@ -0,0 +1 @@
+greet

README.md

@@ -1,3 +1,32 @@
 # Greetings
 
-Greetings is a simple Go program that greets you.
+## Summary
+
+Greet is a simple Go CLI application that greets a recipient.
+This is a simple project used for the purpose of testing upcoming automation,
+such as CI/CD integration and dependency management, which will be used by other projects
+hosted in Code Flow.
+
+## Requirements
+
+- [Go](https://go.dev/)
+
+## Build
+
+```
+$ go build -o greet .
+```
+
+## Run
+
+Greet the world.
+```
+$ ./greet
+Hello, World!
+```
+
+Greet a person.
+```
+$ ./greet Bob
+Hello, Bob!
+```

go.mod

@@ -0,0 +1,3 @@
+module forge.dananglin.me.uk/code/dananglin/greet
+
+go 1.17

greet.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"io"
+)
+
+func main() {
+	osArgs := os.Args[1:]
+
+	if err := greet(os.Stdout, osArgs); err != nil {
+		fmt.Printf("ERROR: %s.\n", err)
+	}
+}
+
+func greet(w io.Writer, n []string) error {
+	var name string
+
+	if len(n) > 1 {
+		return fmt.Errorf("unexpected number of arguments passed to the greeter: want 0 or 1 argument, got %d", len(n))
+	} else if len(n) == 0 {
+		name = "World"
+	} else {
+		name = n[0]
+	}
+
+	fmt.Fprintf(w, "Hello, %s!\n", name)
+
+	return nil
+}

greet_test.go

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"bytes"
+	"testing"
+)
+
+// TestGreetNoArguments tests the greeter's response when given no names.
+func TestGreetNoArguments(t *testing.T) {
+	buffer := new(bytes.Buffer)
+	args := make([]string, 0)
+
+	if err := greet(buffer, args); err != nil {
+		t.Fatalf("an error occured while running greet(): %s", err)
+	}
+
+	want := "Hello, World!\n"
+	got := buffer.String()
+
+	if want != got {
+		t.Errorf("unexpected output returned from greet(): want '%s', got '%s'", want, got)
+	} else {
+		t.Logf("expected output returned from greet(): got '%s'", got)
+	}
+}
+
+// TestGreetOneArgument tests the greeter's response when given one name.
+func TestGreetOneArgument(t *testing.T) {
+	buffer := new(bytes.Buffer)
+	args := []string{"Sarah"}
+
+	if err := greet(buffer, args); err != nil {
+		t.Fatalf("an error occured while running greet(): %s", err)
+	}
+
+	want := "Hello, Sarah!\n"
+	got := buffer.String()
+
+	if want != got {
+		t.Errorf("unexpected output returned from greet(): want '%s', got '%s'", want, got)
+	} else {
+		t.Logf("expected output returned from greet(): got '%s'", got)
+	}
+}
+
+// TestGreetTwoArguments tests the greeter's response when given two names.
+func TestGreetTwoArguments(t *testing.T) {
+	buffer := new(bytes.Buffer)
+	args := []string{"Bob", "John"}
+
+	want := "unexpected number of arguments passed to the greeter: want 0 or 1 argument, got 2"
+	
+	err := greet(buffer, args)
+
+	if err == nil {
+		t.Error("unexpected nil error returned.")
+	}
+
+	got := err.Error()
+
+	if want != got {
+		t.Errorf("unexpected error message returned: want '%s', got '%s'", want, got)
+	} else {
+		t.Logf("expected error message returned: got '%s'", got)
+	}
+}