fix(tests): fix config.Paths tests

Refactor `config.Paths` (by externalizing a call to `homedir.Dir`) to
decouple it from filesystem paths, thus facilitating cleaner unit-tests.

cmd/cheat/main.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 
 	"github.com/docopt/docopt-go"
+	"github.com/mitchellh/go-homedir"
 
 	"github.com/cheat/cheat/internal/cheatpath"
 	"github.com/cheat/cheat/internal/config"
@@ -34,6 +35,13 @@ func main() {
 		os.Exit(0)
 	}
 
+	// get the user's home directory
+	home, err := homedir.Dir()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "failed to get user home directory: %v\n", err)
+		os.Exit(1)
+	}
+
 	// read the envvars into a map of strings
 	envvars := map[string]string{}
 	for _, e := range os.Environ() {
@@ -42,7 +50,7 @@ func main() {
 	}
 
 	// load the os-specifc paths at which the config file may be located
-	confpaths, err := config.Paths(runtime.GOOS, envvars)
+	confpaths, err := config.Paths(runtime.GOOS, home, envvars)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "failed to load config: %v\n", err)
 		os.Exit(1)

internal/config/paths.go

@@ -9,13 +9,11 @@ import (
 
 // Paths returns config file paths that are appropriate for the operating
 // system
-func Paths(sys string, envvars map[string]string) ([]string, error) {
-
-	// get the user's home directory
-	home, err := homedir.Dir()
-	if err != nil {
-		return []string{}, fmt.Errorf("failed to get user home directory: %v", err)
-	}
+func Paths(
+	sys string,
+	home string,
+	envvars map[string]string,
+) ([]string, error) {
 
 	// if `CHEAT_CONFIG_PATH` is set, expand ~ and return it
 	if confpath, ok := envvars["CHEAT_CONFIG_PATH"]; ok {

internal/config/paths_test.go

@@ -11,9 +11,11 @@ import (
 // *nix platforms
 func TestValidatePathsNix(t *testing.T) {
 
+	// mock the user's home directory
+	home := "/home/foo"
+
 	// mock some envvars
 	envvars := map[string]string{
-		"HOME":            "/home/foo",
 		"XDG_CONFIG_HOME": "/home/bar",
 	}
 
@@ -27,7 +29,7 @@ func TestValidatePathsNix(t *testing.T) {
 	// test each *nix os
 	for _, os := range oses {
 		// get the paths for the platform
-		paths, err := Paths(os, envvars)
+		paths, err := Paths(os, home, envvars)
 		if err != nil {
 			t.Errorf("paths returned an error: %v", err)
 		}
@@ -54,10 +56,11 @@ func TestValidatePathsNix(t *testing.T) {
 // on *nix platforms when `XDG_CONFIG_HOME is not set
 func TestValidatePathsNixNoXDG(t *testing.T) {
 
+	// mock the user's home directory
+	home := "/home/foo"
+
 	// mock some envvars
-	envvars := map[string]string{
-		"HOME": "/home/foo",
-	}
+	envvars := map[string]string{}
 
 	// specify the platforms to test
 	oses := []string{
@@ -69,7 +72,7 @@ func TestValidatePathsNixNoXDG(t *testing.T) {
 	// test each *nix os
 	for _, os := range oses {
 		// get the paths for the platform
-		paths, err := Paths(os, envvars)
+		paths, err := Paths(os, home, envvars)
 		if err != nil {
 			t.Errorf("paths returned an error: %v", err)
 		}
@@ -95,6 +98,9 @@ func TestValidatePathsNixNoXDG(t *testing.T) {
 // on Windows platforms
 func TestValidatePathsWindows(t *testing.T) {
 
+	// mock the user's home directory
+	home := "not-used-on-windows"
+
 	// mock some envvars
 	envvars := map[string]string{
 		"APPDATA":     "/apps",
@@ -102,7 +108,7 @@ func TestValidatePathsWindows(t *testing.T) {
 	}
 
 	// get the paths for the platform
-	paths, err := Paths("windows", envvars)
+	paths, err := Paths("windows", home, envvars)
 	if err != nil {
 		t.Errorf("paths returned an error: %v", err)
 	}
@@ -126,7 +132,7 @@ func TestValidatePathsWindows(t *testing.T) {
 // TestValidatePathsUnsupported asserts that an error is returned on
 // unsupported platforms
 func TestValidatePathsUnsupported(t *testing.T) {
-	_, err := Paths("unsupported", map[string]string{})
+	_, err := Paths("unsupported", "", map[string]string{})
 	if err == nil {
 		t.Errorf("failed to return error on unsupported platform")
 	}
@@ -136,15 +142,17 @@ func TestValidatePathsUnsupported(t *testing.T) {
 // returned when `CHEAT_CONFIG_PATH` is explicitly specified.
 func TestValidatePathsCheatConfigPath(t *testing.T) {
 
+	// mock the user's home directory
+	home := "/home/foo"
+
 	// mock some envvars
 	envvars := map[string]string{
-		"HOME":              "/home/foo",
 		"XDG_CONFIG_HOME":   "/home/bar",
 		"CHEAT_CONFIG_PATH": "/home/baz/conf.yml",
 	}
 
 	// get the paths for the platform
-	paths, err := Paths("linux", envvars)
+	paths, err := Paths("linux", home, envvars)
 	if err != nil {
 		t.Errorf("paths returned an error: %v", err)
 	}