add tests

viewport/viewport.go

@@ -10,6 +10,10 @@ import (
 	"github.com/mattn/go-runewidth"
 )
 
+const (
+	defaultHorizontalStep = 5
+)
+
 // New returns a new model with the given width and height as well as default
 // key mappings.
 func New(width, height int) (m Model) {
@@ -68,7 +72,7 @@ func (m *Model) setInitialValues() {
 	m.MouseWheelEnabled = true
 	m.MouseWheelDelta = 3
 	m.initialized = true
-	m.horizontalStep = 5
+	m.horizontalStep = defaultHorizontalStep
 }
 
 // Init exists to satisfy the tea.Model interface for composability purposes.

viewport/viewport_test.go

@@ -0,0 +1,295 @@
+package viewport
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestNew(t *testing.T) {
+	t.Parallel()
+
+	t.Run("default values on create by New", func(t *testing.T) {
+		t.Parallel()
+
+		m := New(10, 10)
+
+		if !m.initialized {
+			t.Errorf("on create by New Model should be initialized")
+		}
+
+		if m.horizontalStep != defaultHorizontalStep {
+			t.Errorf("default horizontalStep should be %d, got %d", defaultHorizontalStep, m.horizontalStep)
+		}
+
+		if m.MouseWheelDelta != 3 {
+			t.Errorf("default MouseWheelDelta should be 3, got %d", m.MouseWheelDelta)
+		}
+
+		if !m.MouseWheelEnabled {
+			t.Error("mouse wheel should be enabled by default")
+		}
+	})
+}
+
+func TestSetInitialValues(t *testing.T) {
+	t.Parallel()
+
+	t.Run("default horizontalStep", func(t *testing.T) {
+		t.Parallel()
+
+		m := Model{}
+		m.setInitialValues()
+
+		if m.horizontalStep != defaultHorizontalStep {
+			t.Errorf("default horizontalStep should be %d, got %d", defaultHorizontalStep, m.horizontalStep)
+		}
+	})
+}
+
+func TestSetHorizontalStep(t *testing.T) {
+	t.Parallel()
+
+	t.Run("change default", func(t *testing.T) {
+		t.Parallel()
+
+		m := New(10, 10)
+
+		if m.horizontalStep != defaultHorizontalStep {
+			t.Errorf("default horizontalStep should be %d, got %d", defaultHorizontalStep, m.horizontalStep)
+		}
+
+		newStep := 8
+		m.SetHorizontalStep(newStep)
+		if m.horizontalStep != newStep {
+			t.Errorf("horizontalStep should be %d, got %d", newStep, m.horizontalStep)
+		}
+	})
+
+	t.Run("no negative", func(t *testing.T) {
+		t.Parallel()
+
+		m := New(10, 10)
+
+		if m.horizontalStep != defaultHorizontalStep {
+			t.Errorf("default horizontalStep should be %d, got %d", defaultHorizontalStep, m.horizontalStep)
+		}
+
+		zero := 0
+		m.SetHorizontalStep(-1)
+		if m.horizontalStep != zero {
+			t.Errorf("horizontalStep should be %d, got %d", zero, m.horizontalStep)
+		}
+	})
+}
+
+func TestMoveLeft(t *testing.T) {
+	t.Parallel()
+
+	zeroPosition := 0
+
+	t.Run("zero position", func(t *testing.T) {
+		t.Parallel()
+
+		m := New(10, 10)
+		if m.indent != zeroPosition {
+			t.Errorf("default indent should be %d, got %d", zeroPosition, m.indent)
+		}
+
+		m.MoveLeft()
+		if m.indent != zeroPosition {
+			t.Errorf("indent should be %d, got %d", zeroPosition, m.indent)
+		}
+	})
+
+	t.Run("move", func(t *testing.T) {
+		t.Parallel()
+		m := New(10, 10)
+		if m.indent != zeroPosition {
+			t.Errorf("default indent should be %d, got %d", zeroPosition, m.indent)
+		}
+
+		m.indent = defaultHorizontalStep * 2
+		m.MoveLeft()
+		newIndent := defaultHorizontalStep
+		if m.indent != newIndent {
+			t.Errorf("indent should be %d, got %d", newIndent, m.indent)
+		}
+	})
+}
+
+func TestMoveRight(t *testing.T) {
+	t.Parallel()
+
+	t.Run("move", func(t *testing.T) {
+		t.Parallel()
+
+		zeroPosition := 0
+
+		m := New(10, 10)
+		if m.indent != zeroPosition {
+			t.Errorf("default indent should be %d, got %d", zeroPosition, m.indent)
+		}
+
+		m.MoveRight()
+		newIndent := defaultHorizontalStep
+		if m.indent != newIndent {
+			t.Errorf("indent should be %d, got %d", newIndent, m.indent)
+		}
+	})
+}
+
+func TestResetIndent(t *testing.T) {
+	t.Parallel()
+
+	t.Run("reset", func(t *testing.T) {
+		t.Parallel()
+
+		zeroPosition := 0
+
+		m := New(10, 10)
+		m.indent = 500
+
+		m.ResetIndent()
+		if m.indent != zeroPosition {
+			t.Errorf("indent should be %d, got %d", zeroPosition, m.indent)
+		}
+	})
+}
+
+func TestVisibleLines(t *testing.T) {
+	t.Parallel()
+
+	defaultList := []string{
+		`57 Precepts of narcissistic comedy character Zote from an awesome "Hollow knight" game (https://store.steampowered.com/app/367520/Hollow_Knight/).`,
+		`Precept One: 'Always Win Your Battles'. Losing a battle earns you nothing and teaches you nothing. Win your battles, or don't engage in them at all!`,
+		`Precept Two: 'Never Let Them Laugh at You'. Fools laugh at everything, even at their superiors. But beware, laughter isn't harmless! Laughter spreads like a disease, and soon everyone is laughing at you. You need to strike at the source of this perverse merriment quickly to stop it from spreading.`,
+		`Precept Three: 'Always Be Rested'. Fighting and adventuring take their toll on your body. When you rest, your body strengthens and repairs itself. The longer you rest, the stronger you become.`,
+		`Precept Four: 'Forget Your Past'. The past is painful, and thinking about your past can only bring you misery. Think about something else instead, such as the future, or some food.`,
+		`Precept Five: 'Strength Beats Strength'. Is your opponent strong? No matter! Simply overcome their strength with even more strength, and they'll soon be defeated.`,
+		`Precept Six: 'Choose Your Own Fate'. Our elders teach that our fate is chosen for us before we are even born. I disagree.`,
+		`Precept Seven: 'Mourn Not the Dead'. When we die, do things get better for us or worse? There's no way to tell, so we shouldn't bother mourning. Or celebrating for that matter.`,
+		`Precept Eight: 'Travel Alone'. You can rely on nobody, and nobody will always be loyal. Therefore, nobody should be your constant companion.`,
+		`Precept Nine: 'Keep Your Home Tidy'. Your home is where you keep your most prized possession - yourself. Therefore, you should make an effort to keep it nice and clean.`,
+		`Precept Ten: 'Keep Your Weapon Sharp'. I make sure that my weapon, 'Life Ender', is kept well-sharpened at all times. This makes it much easier to cut things.`,
+		`Precept Eleven: 'Mothers Will Always Betray You'. This Precept explains itself.`,
+		`Precept Twelve: 'Keep Your Cloak Dry'. If your cloak gets wet, dry it as soon as you can. Wearing wet cloaks is unpleasant, and can lead to illness.`,
+		`Precept Thirteen: 'Never Be Afraid'. Fear can only hold you back. Facing your fears can be a tremendous effort. Therefore, you should just not be afraid in the first place.`,
+		`Precept Fourteen: 'Respect Your Superiors'. If someone is your superior in strength or intellect or both, you need to show them your respect. Don't ignore them or laugh at them.`,
+		`Precept Fifteen: 'One Foe, One Blow'. You should only use a single blow to defeat an enemy. Any more is a waste. Also, by counting your blows as you fight, you'll know how many foes you've defeated.`,
+		`...`,
+	}
+
+	t.Run("empty list", func(t *testing.T) {
+		t.Parallel()
+
+		m := New(10, 10)
+		list := m.visibleLines()
+
+		if len(list) != 0 {
+			t.Errorf("list should be empty, got %d", len(list))
+		}
+	})
+
+	t.Run("empty list: with indent", func(t *testing.T) {
+		t.Parallel()
+
+		m := New(10, 10)
+		list := m.visibleLines()
+		m.indent = 5
+
+		if len(list) != 0 {
+			t.Errorf("list should be empty, got %d", len(list))
+		}
+	})
+
+	t.Run("list", func(t *testing.T) {
+		t.Parallel()
+		numberOfLines := 10
+
+		m := New(10, numberOfLines)
+		m.lines = defaultList
+
+		list := m.visibleLines()
+		if len(list) != numberOfLines {
+			t.Errorf("list should have %d lines, got %d", numberOfLines, len(list))
+		}
+
+		lastItem := numberOfLines - 1
+		if list[lastItem] != defaultList[lastItem] {
+			t.Errorf("%dth list item should the the same as %dth default list item", lastItem, lastItem)
+		}
+	})
+
+	t.Run("list: with y offset", func(t *testing.T) {
+		t.Parallel()
+		numberOfLines := 10
+
+		m := New(10, numberOfLines)
+		m.lines = defaultList
+		m.YOffset = 5
+
+		list := m.visibleLines()
+		if len(list) != numberOfLines {
+			t.Errorf("list should have %d lines, got %d", numberOfLines, len(list))
+		}
+
+		if list[0] == defaultList[0] {
+			t.Error("first item of list should not be the first item of initial list because of Y offset")
+		}
+
+		lastItem := numberOfLines - 1
+		if list[lastItem] != defaultList[m.YOffset+lastItem] {
+			t.Errorf("%dth list item should the the same as %dth default list item", lastItem, lastItem)
+		}
+	})
+
+	t.Run("list: with y offset: horizontal scroll", func(t *testing.T) {
+		t.Parallel()
+		numberOfLines := 10
+
+		m := New(10, numberOfLines)
+		m.lines = defaultList
+		m.YOffset = 7
+
+		// default list
+		list := m.visibleLines()
+		if len(list) != numberOfLines {
+			t.Errorf("list should have %d lines, got %d", numberOfLines, len(list))
+		}
+
+		lastItem := numberOfLines - 1
+		defaultLastItem := len(defaultList) - 1
+		if list[lastItem] != defaultList[defaultLastItem] {
+			t.Errorf("%dth list item should the the same as %dth default list item", lastItem, defaultLastItem)
+		}
+
+		perceptPrefix := "Precept"
+		if !strings.HasPrefix(list[0], perceptPrefix) {
+			t.Errorf("first list item has to have prefix %s", perceptPrefix)
+		}
+
+		// move right
+		m.MoveRight()
+		list = m.visibleLines()
+
+		newPrefix := perceptPrefix[m.indent:]
+		if !strings.HasPrefix(list[0], newPrefix) {
+			t.Errorf("first list item has to have prefix %s, get %s", newPrefix, list[0])
+		}
+
+		if list[lastItem] != "" {
+			t.Errorf("last item should be empty, got %s", list[lastItem])
+		}
+
+		// move left
+		m.MoveLeft()
+		list = m.visibleLines()
+		if !strings.HasPrefix(list[0], perceptPrefix) {
+			t.Errorf("first list item has to have prefix %s", perceptPrefix)
+		}
+
+		if list[lastItem] != defaultList[defaultLastItem] {
+			t.Errorf("%dth list item should the the same as %dth default list item", lastItem, defaultLastItem)
+		}
+	})
+}