Add FilePath TestCases

- Added a test case and example test for the NewFilePath function

filepath_test.go

@@ -0,0 +1,59 @@
+package moibit
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+	"testing"
+)
+
+func ExampleNewFilePath() {
+	directory := "appdata/users"
+	filename := "userdata.json"
+
+	fp, _ := NewFilePath(directory, filename)
+	fmt.Println("Path:", fp)
+
+	// Output:
+	// Path: /appdata/users/userdata.json
+}
+
+func TestNewFilePath(t *testing.T) {
+	tests := []struct {
+		input []string
+		path  string
+		error error
+	}{
+		{[]string{"data", "devices"}, "/data/devices", nil},
+		{[]string{"//data", "devices/", "hello.txt"}, "/data/devices/hello.txt", nil},
+		{[]string{"data/devices", "hello.txt"}, "/data/devices/hello.txt", nil},
+		{[]string{"/data"}, "/data", nil},
+		{[]string{"/data", ""}, "/data", nil},
+		{[]string{"data", "/devices"}, "/data/devices", nil},
+		{[]string{"data/", "/devices/hello.txt"}, "/data/devices/hello.txt", nil},
+		{
+			[]string{"data", "/devices.txt/hello"}, "/",
+			errors.New("failed to construct filepath: slash detected after period or missing extension"),
+		},
+		{
+			[]string{"data", "/devices.txt/hello.txt"}, "/",
+			errors.New("failed to construct filepath: multiple periods in final element"),
+		},
+		{
+			[]string{"dat.txt", "/devices.txt/hello.txt"}, "/",
+			errors.New("failed to construct filepath: non-final element '0' contains period"),
+		},
+	}
+
+	for _, test := range tests {
+		fp, err := NewFilePath(test.input...)
+
+		if !reflect.DeepEqual(err, test.error) {
+			t.Fatalf("error mismatch. expected: %v. got: %v", test.error, err)
+		}
+
+		if !reflect.DeepEqual(test.path, fp.Path()) {
+			t.Fatalf("path mismatch. expected: %v. got: %v", test.path, fp.Path())
+		}
+	}
+}