run npm install to generate a package lock

node_modules/@weborigami/async-tree/test/operations/merge.test.js

@@ -0,0 +1,64 @@
+import assert from "node:assert";
+import { describe, test } from "node:test";
+import { DeepObjectTree, ObjectTree, Tree } from "../../src/internal.js";
+import merge from "../../src/operations/merge.js";
+import * as symbols from "../../src/symbols.js";
+
+describe("merge", () => {
+  test("performs a shallow merge", async () => {
+    const fixture = merge(
+      {
+        a: 1,
+        // Will be obscured by `b` that follows
+        b: {
+          c: 2,
+        },
+      },
+      {
+        b: {
+          d: 3,
+        },
+        e: {
+          f: 4,
+        },
+      }
+    );
+
+    assert.deepEqual(await Tree.plain(fixture), {
+      a: 1,
+      b: {
+        d: 3,
+      },
+      e: {
+        f: 4,
+      },
+    });
+
+    // Merge is shallow, and last tree wins, so `b/c` doesn't exist
+    const c = await Tree.traverse(fixture, "b", "c");
+    assert.equal(c, undefined);
+
+    // Parent of a subvalue is the merged tree
+    const b = await fixture.get("b");
+    assert.equal(b[symbols.parent], fixture);
+  });
+
+  test("subtree can overwrite a leaf node", async () => {
+    const fixture = merge(
+      new ObjectTree({
+        a: 1,
+      }),
+      new DeepObjectTree({
+        a: {
+          b: 2,
+        },
+      })
+    );
+    assert.deepEqual([...(await fixture.keys())], ["a/"]);
+    assert.deepEqual(await Tree.plain(fixture), {
+      a: {
+        b: 2,
+      },
+    });
+  });
+});