lets not do closures on chapter 1

Author: quii

arrays-and-slices.md

@@ -504,7 +504,7 @@ func SumAllTails(numbersToSum ...[]int) []int {
 
 ## Refactor
 
-Our tests have some repeated code around the assertions again, so let's extract those into a function
+Our tests have some repeated code around the assertions again, so let's extract those into a function.
 
 ```go
 func TestSumAllTails(t *testing.T) {
@@ -531,6 +531,12 @@ func TestSumAllTails(t *testing.T) {
 }
 ```
 
+We could've created a new function `checkSums` like we normally do, but in this case, we're showing a new technique, assigning a function to a variable. It might look strange but, it's no different to assigning a variable to a `string`, or an `int`, functions in effect are values too. 
+
+It's not shown here, but this technique can be useful when you want to bind a function to other local variables in "scope" (e.g between some `{}`). It also allows you to reduce the surface area of your API. 
+
+By defining this function inside the test, it cannot be used by other functions in this package. Hiding variables and functions that don't need to be exported is an important design consideration.
+
 A handy side-effect of this is this adds a little type-safety to our code. If
 a developer mistakenly adds a new test with `checkSums(t, got, "dave")` the compiler
 will stop them in their tracks.

hello-world.md

@@ -275,31 +275,33 @@ We can and should refactor our tests.
 
 ```go
 func TestHello(t *testing.T) {
-	assertCorrectMessage := func(t testing.TB, got, want string) {
-		t.Helper()
-		if got != want {
-			t.Errorf("got %q want %q", got, want)
-		}
-	}
-
 	t.Run("saying hello to people", func(t *testing.T) {
 		got := Hello("Chris")
 		want := "Hello, Chris"
 		assertCorrectMessage(t, got, want)
 	})
-	t.Run("empty string defaults to 'World'", func(t *testing.T) {
+
+	t.Run("empty string defaults to 'world'", func(t *testing.T) {
 		got := Hello("")
 		want := "Hello, World"
 		assertCorrectMessage(t, got, want)
 	})
+
+}
+
+func assertCorrectMessage(t testing.TB, got, want string) {
+	t.Helper()
+	if got != want {
+		t.Errorf("got %q want %q", got, want)
+	}
 }
 ```
 
 What have we done here?
 
-We've refactored our assertion into a function. This reduces duplication and improves readability of our tests. In Go you can declare functions inside other functions and assign them to variables. You can then call them, just like normal functions. We need to pass in `t *testing.T` so that we can tell the test code to fail when we need to.
+We've refactored our assertion into a new function. This reduces duplication and improves readability of our tests. We need to pass in `t *testing.T` so that we can tell the test code to fail when we need to.
 
-For helper functions, it's a good idea to accept a `testing.TB` which is an interface that `*testing.T` and `*testing.B` both satisfy, so you can call helper functions from a test, or a benchmark.
+For helper functions, it's a good idea to accept a `testing.TB` which is an interface that `*testing.T` and `*testing.B` both satisfy, so you can call helper functions from a test, or a benchmark (don't worry if words like "interface" mean nothing to you right now, it will be covered later).
 
 `t.Helper()` is needed to tell the test suite that this method is a helper. By doing this when it fails the line number reported will be in our _function call_ rather than inside our test helper. This will help other developers track down problems easier. If you still don't understand, comment it out, make a test fail and observe the test output. Comments in Go are a great way to add additional information to your code, or in this case, a quick way to tell the compiler to ignore a line. You can comment out the `t.Helper()` code by adding two forward slashes `//` at the beginning of the line. You should see that line turn grey or change to another color than the rest of your code to indicate it's now commented out.
 

hello-world/v5/hello_test.go

@@ -3,14 +3,6 @@ package main
 import "testing"
 
 func TestHello(t *testing.T) {
-
-	assertCorrectMessage := func(t testing.TB, got, want string) {
-		t.Helper()
-		if got != want {
-			t.Errorf("got %q want %q", got, want)
-		}
-	}
-
 	t.Run("saying hello to people", func(t *testing.T) {
 		got := Hello("Chris")
 		want := "Hello, Chris"
@@ -24,3 +16,10 @@ func TestHello(t *testing.T) {
 	})
 
 }
+
+func assertCorrectMessage(t testing.TB, got, want string) {
+	t.Helper()
+	if got != want {
+		t.Errorf("got %q want %q", got, want)
+	}
+}

hello-world/v6/hello_test.go

@@ -3,14 +3,6 @@ package main
 import "testing"
 
 func TestHello(t *testing.T) {
-
-	assertCorrectMessage := func(t testing.TB, got, want string) {
-		t.Helper()
-		if got != want {
-			t.Errorf("got %q want %q", got, want)
-		}
-	}
-
 	t.Run("to a person", func(t *testing.T) {
 		got := Hello("Chris", "")
 		want := "Hello, Chris"
@@ -36,3 +28,10 @@ func TestHello(t *testing.T) {
 	})
 
 }
+
+func assertCorrectMessage(t testing.TB, got, want string) {
+	t.Helper()
+	if got != want {
+		t.Errorf("got %q want %q", got, want)
+	}
+}

hello-world/v7/hello_test.go

@@ -3,36 +3,34 @@ package main
 import "testing"
 
 func TestHello(t *testing.T) {
-
-	assertCorrectMessage := func(got, want string) {
-		t.Helper()
-		if got != want {
-			t.Errorf("got %q want %q", got, want)
-		}
-	}
-
 	t.Run("saying hello to people", func(t *testing.T) {
 		got := Hello("Chris", "")
 		want := "Hello, Chris"
-		assertCorrectMessage(got, want)
+		assertCorrectMessage(t, got, want)
 	})
 
 	t.Run("say hello world when an empty string is supplied", func(t *testing.T) {
 		got := Hello("", "")
 		want := "Hello, World"
-		assertCorrectMessage(got, want)
+		assertCorrectMessage(t, got, want)
 	})
 
 	t.Run("say hello in Spanish", func(t *testing.T) {
 		got := Hello("Elodie", spanish)
 		want := "Hola, Elodie"
-		assertCorrectMessage(got, want)
+		assertCorrectMessage(t, got, want)
 	})
 
 	t.Run("say hello in French", func(t *testing.T) {
 		got := Hello("Lauren", french)
 		want := "Bonjour, Lauren"
-		assertCorrectMessage(got, want)
+		assertCorrectMessage(t, got, want)
 	})
+}
 
+func assertCorrectMessage(t testing.TB, got, want string) {
+	t.Helper()
+	if got != want {
+		t.Errorf("got %q want %q", got, want)
+	}
 }

hello-world/v8/hello_test.go

@@ -3,14 +3,6 @@ package main
 import "testing"
 
 func TestHello(t *testing.T) {
-
-	assertCorrectMessage := func(t testing.TB, got, want string) {
-		t.Helper()
-		if got != want {
-			t.Errorf("got %q want %q", got, want)
-		}
-	}
-
 	t.Run("to a person", func(t *testing.T) {
 		got := Hello("Chris", "")
 		want := "Hello, Chris"
@@ -34,5 +26,11 @@ func TestHello(t *testing.T) {
 		want := "Bonjour, Lauren"
 		assertCorrectMessage(t, got, want)
 	})
+}
 
+func assertCorrectMessage(t testing.TB, got, want string) {
+	t.Helper()
+	if got != want {
+		t.Errorf("got %q want %q", got, want)
+	}
 }