Test for GROUP BY with no matching rows to confirm #79 is fixed (#2300)

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: mathiasrw <[email protected]>
Co-authored-by: Mathias Wulff <[email protected]>

Author: Copilot

test/test79-B.js

@@ -0,0 +1,64 @@
+if (typeof exports === 'object') {
+	var assert = require('assert');
+	var alasql = require('..');
+}
+
+describe('Test 79-B - GROUP BY with no matching rows', function () {
+	const test = '79-B';
+
+	it('A) GROUP BY returns empty result when no rows meet condition', function () {
+		// Original issue: SELECT with GROUP BY should return [] when WHERE clause matches no rows
+		var res = alasql('SELECT Name FROM ? WHERE 1=0 GROUP BY Name', [[{Name: 'test'}]]);
+		assert.deepEqual(res, []);
+	});
+
+	it('B) GROUP BY with aggregate returns empty result when no rows meet condition', function () {
+		var res = alasql('SELECT Name, COUNT(*) as cnt FROM ? WHERE 1=0 GROUP BY Name', [
+			[{Name: 'test'}],
+		]);
+		assert.deepEqual(res, []);
+	});
+
+	it('C) GROUP BY on empty dataset returns empty result', function () {
+		var res = alasql('SELECT Name FROM ? GROUP BY Name', [[]]);
+		assert.deepEqual(res, []);
+	});
+
+	it('D) GROUP BY with multiple columns and no matches returns empty result', function () {
+		var res = alasql('SELECT Name, Type FROM ? WHERE 1=0 GROUP BY Name, Type', [
+			[{Name: 'test', Type: 'A'}],
+		]);
+		assert.deepEqual(res, []);
+	});
+
+	it('E) Aggregate without GROUP BY returns one row with default values when no rows match', function () {
+		// This is the correct SQL behavior - aggregates without GROUP BY return one row
+		var res = alasql('SELECT COUNT(*) as cnt FROM ? WHERE 1=0', [[{Name: 'test'}]]);
+		assert.deepEqual(res, [{cnt: 0}]);
+	});
+
+	it('F) Aggregate without GROUP BY on empty dataset returns one row', function () {
+		// This is the correct SQL behavior - aggregates without GROUP BY return one row
+		var res = alasql('SELECT COUNT(*) as cnt FROM ?', [[]]);
+		assert.deepEqual(res, [{cnt: 0}]);
+	});
+
+	it('G) GROUP BY with valid data returns correct results', function () {
+		// Sanity check that GROUP BY still works correctly with matching data
+		var res = alasql('SELECT Name FROM ? WHERE 1=1 GROUP BY Name', [[{Name: 'test'}]]);
+		assert.deepEqual(res, [{Name: 'test'}]);
+	});
+
+	it('H) GROUP BY with multiple groups returns correct results', function () {
+		var data = [
+			{Name: 'Alice', Type: 'A'},
+			{Name: 'Bob', Type: 'B'},
+			{Name: 'Alice', Type: 'A'},
+		];
+		var res = alasql('SELECT Name, COUNT(*) as cnt FROM ? GROUP BY Name ORDER BY Name', [data]);
+		assert.deepEqual(res, [
+			{Name: 'Alice', cnt: 2},
+			{Name: 'Bob', cnt: 1},
+		]);
+	});
+});