Add some tests for GetTextStyle

The tests show that setting a hex color doesn't work; we'll fix that in the next
commit.

pkg/theme/style_test.go

@@ -0,0 +1,65 @@
+package theme
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/gookit/color"
+	"github.com/jesseduffield/lazygit/pkg/gui/style"
+)
+
+func TestGetTextStyle(t *testing.T) {
+	scenarios := []struct {
+		name       string
+		keys       []string
+		background bool
+		expected   style.TextStyle
+	}{
+		{
+			name:       "empty",
+			keys:       []string{""},
+			background: true,
+			expected:   style.New(),
+		},
+		{
+			name:       "named color, fg",
+			keys:       []string{"blue"},
+			background: false,
+			expected:   style.New().SetFg(style.NewBasicColor(color.FgBlue)),
+		},
+		{
+			name:       "named color, bg",
+			keys:       []string{"blue"},
+			background: true,
+			expected:   style.New().SetBg(style.NewBasicColor(color.BgBlue)),
+		},
+		{
+			name:       "hex color, fg",
+			keys:       []string{"#123456"},
+			background: false,
+			/* EXPECTED:
+			expected:   style.New().SetFg(style.NewRGBColor(color.RGBColor{0x12, 0x34, 0x56, 0})),
+			ACTUAL:
+			*/
+			expected:   style.New(),
+		},
+		{
+			name:       "hex color, bg",
+			keys:       []string{"#abcdef"},
+			background: true,
+			/* EXPECTED:
+			expected:   style.New().SetBg(style.NewRGBColor(color.RGBColor{0xab, 0xcd, 0xef, 1})),
+			ACTUAL:
+			*/
+			expected:   style.New(),
+		},
+	}
+
+	for _, scenario := range scenarios {
+		t.Run(scenario.name, func(t *testing.T) {
+			if actual := GetTextStyle(scenario.keys, scenario.background); !reflect.DeepEqual(actual, scenario.expected) {
+				t.Errorf("GetTextStyle() = %v, expected %v", actual, scenario.expected)
+			}
+		})
+	}
+}