🔬 test: Add simple edge cases to increase coverage.

Author: make-github-pseudonymous-again

test/src/regression/deletion.js

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+import test from 'ava';
+
+import {list} from '@aureooms/js-itertools';
+import {increasing} from '../../fixtures.js';
+import {RedBlackTree} from '../../../src/index.js';
+
+test('Edge case of small list', (t) => {
+	const reference = [5, 3, 2, 6, 7, 8];
+	const tree = RedBlackTree.from(increasing, reference);
+	t.true(tree.remove(3));
+	t.deepEqual(list(tree), [2, 5, 6, 7, 8]);
+});

test/src/regression/root-deletion.js

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+import test from 'ava';
+
+import {increasing} from '../../fixtures.js';
+import {empty} from '../../../src/index.js';
+
+test('root + pred', (t) => {
+	const tree = empty(increasing);
+	t.true(tree.isEmpty());
+	tree.add(0);
+	t.false(tree.isEmpty());
+	tree.add(-1);
+	t.false(tree.isEmpty());
+	tree.remove(0);
+	t.false(tree.isEmpty());
+	tree.remove(-1);
+	t.true(tree.isEmpty());
+});