Add unit tests.

src/core/transform.go

@@ -86,6 +86,14 @@ func NewPerspective(fov, aspect, near, far Float) *Transform {
 	return NewScale(s, s, 1.0).Multiply(NewTransform(pers))
 }
 
+// At returns an element of Transform.
+func (t *Transform) At(i, j int) Float {
+	if i < 0 || j < 0 || i >= 4 || j >= 4 {
+		panic("Index out of bounds!")
+	}
+	return t.mat[i][j]
+}
+
 // Multiply computes the multiplications of Transforms.
 func (t1 *Transform) Multiply(t2 *Transform) *Transform {
 	ret := new(Transform)

src/core/transform_test.go

@@ -0,0 +1,56 @@
+package core
+
+import (
+	"math"
+	"testing"
+)
+
+func TestTransformAt(t *testing.T) {
+	m := NewTransform([4][4]Float{
+		{1, 2, 3, 4},
+		{5, 6, 7, 8},
+		{9, 10, 11, 12},
+		{13, 14, 15, 16},
+	})
+
+	for i := 0; i < 4; i++ {
+		for j := 0; j < 4; j++ {
+			expected := i*4 + j + 1
+			if m.At(i, j) != Float(expected) {
+				t.Errorf("m.At(%d, %d) != %f, detected %d", i, j, expected, m.At(i, j))
+			}
+		}
+	}
+
+	defer func() {
+		if p := recover(); p != nil {
+		}
+	}()
+
+	m.At(-1, -1)
+	t.Error("Out of bounds subscription did not panic.")
+}
+
+func TestTransformInverted(t *testing.T) {
+	m := NewTransform([4][4]Float{
+		{1, 2, 3, 4},
+		{2, 2, 3, 4},
+		{3, 3, 3, 4},
+		{4, 4, 4, 4},
+	})
+
+	mi := m.Multiply(m.Inverted())
+	for i := 0; i < 4; i++ {
+		for j := 0; j < 4; j++ {
+			if i == j {
+				if math.Abs(mi.At(i, j)-1.0) >= Eps {
+					t.Errorf("Matrix inversion failed!")
+				}
+			} else {
+				if math.Abs(mi.At(i, j)) >= Eps {
+					t.Errorf("Matrix inversion failed!")
+				}
+			}
+		}
+	}
+}