Integers and example tests

learn_go_with_tests/README.md

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+# Learn Go with Tests
+
+https://quii.gitbook.io/learn-go-with-tests/
+
+## Modules and Packages
+
+Go source files can only have one package per directory. This is some "outdated advice" so your mileage may vary. Go 1.22 definitely has more capabilities for packages and how your manage source code. https://dave.cheney.net/2014/12/01/five-suggestions-for-setting-up-a-go-project
+
+- Name of a package should match the directory name.
+- All lower case, only letters and numbers, NO punctuation.
+- name of a package is part of the name of every public type, const, variable, etc `Example: mypkg.MyBuffer`. So consider what it looks like to a caller.
+- All files in a package directory must have ethe same package declaration, the exception is test files, _test.go. Test files __may__ declare themselves to be in the same package, but with _test appended to the package declaration. These are known as __external tests__.
+- packages that are actually commands carry the `package main` declaration. The name of the command is taken from the name of the packages directory.
+- The go commands; `go build`, `go install`, `go test`, `go get`, all work with packages, not individual files. `go run` is the exception to this rule. 
+- All packages exist inside a directory tree rooted at $GOPATH/src. Because of this, a package’s import path and a package’s name are often different. The import path is effectively the full path to your package. 
+- In Go, the convention is to include the location of the source code in the package’s import path, ie `$GOPATH/src/github.com/golang/glog` This is not required by the language, it is just a feature of go get.
+
+
+## Testable Examples
+
+https://go.dev/blog/examples
+
+As with typical tests, examples are functions that reside in a package’s _test.go files. Unlike normal test functions, though, example functions take no arguments and begin with the word Example instead of Test.
+
+If your code changes so that the example is no longer valid, your build will fail. Note that the example function will not be executed if you remove the comment // Output: 6. Although the function will be compiled, it won't be executed.
+
+By adding this code the example will appear in the documentation inside godoc, making your code even more accessible.
+
+If you publish your code with examples to a public URL, you can share the documentation of your code at https://pkg.go.dev/

learn_go_with_tests/integers/adder.go

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+package integers
+
+// Add takes two integers and returns the sum of them.
+func Add(x, y int) int {
+	return x + y
+}

learn_go_with_tests/integers/adder_test.go

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+package integers
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestAdder(t *testing.T) {
+	sum := Add(2, 2)
+	expected := 4
+
+	if sum != expected {
+		t.Errorf("Expected '%d', but got '%d'", expected, sum)
+	}
+}
+
+// If your code changes so that the example is no longer valid, your build will fail.
+func ExampleAdd() {
+	sum := Add(1, 5)
+	fmt.Println(sum)
+	// Output: 6
+}

learn_go_with_tests/integers/go.mod

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+module integers
+
+go 1.21.0