Test: Internal exchange coverage (#1525)

* Test: Internal exchange coverage

* Tests: Rename exchange.TestInstance to Setup

This package function is either going to be imported and used as just exchange.Setup,
or more likely testexch.Setup.
This removes the Stutter of having
internal/testing/exchange.TestInstance which is implicit given the
package path

internal/testing/utils/path.go

@@ -0,0 +1,35 @@
+package path
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// Exported public errors
+var (
+	ErrRootNotFound = errors.New("could not find root of gocryptotrader")
+)
+
+// RootPathFromCWD returns the system path to GoCryptoTrader from the current working directory
+// Expects to find LICENSE file
+func RootPathFromCWD() (string, error) {
+	wd, err := os.Getwd()
+	if err != nil {
+		return "", err
+	}
+	return RootPath(wd)
+}
+
+// RootPath returns the system path to GoCryptoTrader from a sub-directory path
+func RootPath(p string) (string, error) {
+	parts := strings.Split(p, string(filepath.Separator))
+	for i := len(parts); i > 0; i-- {
+		dir := strings.Join(parts[:i], string(filepath.Separator))
+		if _, err := os.Stat(filepath.Join(dir, "LICENSE")); err == nil {
+			return dir, nil
+		}
+	}
+	return "", ErrRootNotFound
+}