1 files changed, 126 insertions, 0 deletions
diff --git a/lib/rbtree/rbtree_test.go b/lib/rbtree/rbtree_test.go
new file mode 100644
index 0000000..9b8e02c
--- /dev/null
+++ b/lib/rbtree/rbtree_test.go
@@ -0,0 +1,126 @@
+package rbtree
+
+import (
+	"sort"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"golang.org/x/exp/constraints"
+)
+
+func checkTree[K constraints.Ordered, V any](t *testing.T, expectedSet map[K]struct{}, tree *Tree[K, V]) {
+	// 1. Every node is either red or black
+
+	// 2. The root is black.
+	require.Equal(t, Black, tree.root.getColor())
+
+	// 3. Every nil is black.
+
+	// 4. If a node is red, then both its children are black.
+	require.NoError(t, tree.Walk(func(node *Node[V]) error {
+		if node.getColor() == Red {
+			require.Equal(t, Black, node.Left.getColor())
+			require.Equal(t, Black, node.Right.getColor())
+		}
+		return nil
+	}))
+
+	// 5. For each node, all simple paths from the node to
+	//    descendent leaves contain the same number of black
+	//    nodes.
+	var walkCnt func(node *Node[V], cnt int, leafFn func(int))
+	walkCnt = func(node *Node[V], cnt int, leafFn func(int)) {
+		if node.getColor() == Black {
+			cnt++
+		}
+		if node == nil {
+			leafFn(cnt)
+			return
+		}
+		walkCnt(node.Left, cnt, leafFn)
+		walkCnt(node.Right, cnt, leafFn)
+	}
+	require.NoError(t, tree.Walk(func(node *Node[V]) error {
+		var cnts []int
+		walkCnt(node, 0, func(cnt int) {
+			cnts = append(cnts, cnt)
+		})
+		for i := range cnts {
+			if cnts[0] != cnts[i] {
+				require.Truef(t, false, "node %v: not all leafs have same black-count: %v", node.Value, cnts)
+				break
+			}
+		}
+		return nil
+	}))
+
+	// expected contents
+	expectedOrder := make([]K, 0, len(expectedSet))
+	for k := range expectedSet {
+		expectedOrder = append(expectedOrder, k)
+		node := tree.Lookup(k)
+		require.NotNil(t, tree, node)
+		require.Equal(t, k, tree.KeyFn(node.Value))
+	}
+	sort.Slice(expectedOrder, func(i, j int) bool {
+		return expectedOrder[i] < expectedOrder[j]
+	})
+	actOrder := make([]K, 0, len(expectedSet))
+	require.NoError(t, tree.Walk(func(node *Node[V]) error {
+		actOrder = append(actOrder, tree.KeyFn(node.Value))
+		return nil
+	}))
+	require.Equal(t, expectedOrder, actOrder)
+}
+
+func FuzzTree(f *testing.F) {
+	Ins := uint8(0b0100_0000)
+	Del := uint8(0)
+
+	f.Add([]uint8{})
+	f.Add([]uint8{Ins | 5, Del | 5})
+	f.Add([]uint8{Ins | 5, Del | 6})
+	f.Add([]uint8{Del | 6})
+
+	f.Add([]uint8{ // CLRS Figure 14.4
+		Ins | 1,
+		Ins | 2,
+		Ins | 5,
+		Ins | 7,
+		Ins | 8,
+		Ins | 11,
+		Ins | 14,
+		Ins | 15,
+
+		Ins | 4,
+	})
+
+	f.Fuzz(func(t *testing.T, dat []uint8) {
+		tree := &Tree[uint8, uint8]{
+			KeyFn: func(x uint8) uint8 { return x },
+		}
+		set := make(map[uint8]struct{})
+		checkTree(t, set, tree)
+		t.Logf("\n%s\n", tree.ASCIIArt())
+		for _, b := range dat {
+			ins := (b & 0b0100_0000) != 0
+			val := (b & 0b0011_1111)
+			if ins {
+				t.Logf("Insert(%v)", val)
+				tree.Insert(val)
+				set[val] = struct{}{}
+				t.Logf("\n%s\n", tree.ASCIIArt())
+				node := tree.Lookup(val)
+				require.NotNil(t, node)
+				require.Equal(t, val, node.Value)
+			} else {
+				t.Logf("Delete(%v)", val)
+				tree.Delete(val)
+				delete(set, val)
+				t.Logf("\n%s\n", tree.ASCIIArt())
+				require.Nil(t, tree.Lookup(val))
+			}
+			checkTree(t, set, tree)
+		}
+	})
+}