initial

internal/puzzle/puzzle_test.go

@@ -0,0 +1,58 @@
+package puzzle_test
+
+import (
+	"15-puzzle/internal/puzzle"
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsSolvable(t *testing.T) {
+	table := []struct {
+		puzzle   [16]byte
+		solvable bool
+	}{
+		{[16]byte{
+			13, 2, 10, 3,
+			1, 12, 8, 4,
+			5, 0, 9, 6,
+			15, 14, 11, 7},
+			true},
+		{[16]byte{
+			6, 13, 7, 10,
+			8, 9, 11, 0,
+			15, 2, 12, 5,
+			14, 3, 1, 4},
+			true},
+		{[16]byte{
+			12, 1, 10, 2,
+			7, 11, 4, 14,
+			5, 0, 9, 15,
+			8, 13, 6, 3},
+			true},
+		{[16]byte{ // not solvable permutation
+			3, 9, 1, 15,
+			14, 11, 4, 6,
+			13, 0, 10, 12,
+			2, 7, 8, 5},
+			false},
+		{[16]byte{ // same as before but tiles 1 and 2 are switched
+			3, 9, 2, 15,
+			14, 11, 4, 6,
+			13, 0, 10, 12,
+			1, 7, 8, 5},
+			true},
+	}
+	for i := range table {
+		t.Run(fmt.Sprintf("case_%d", i), func(t *testing.T) {
+			solvable, err := puzzle.IsSolvable(table[i].puzzle)
+			assert.NoError(t, err)
+			assert.Equal(t, table[i].solvable, solvable)
+		})
+	}
+	_, err := puzzle.IsSolvable([16]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 11, 13, 14, 15, 16})
+	assert.Error(t, err)
+	_, err = puzzle.IsSolvable([16]byte{0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0})
+	assert.Error(t, err)
+}