adding tests to StickyHeader and StickyHeaderWidgetBuilder

test/sticky_headers/widget_test.dart

@@ -0,0 +1,95 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:sticky_headers/sticky_headers/widget.dart';
+
+void main() {
+  group('OverlapHeaders ', () {
+    testWidgets('defaults to false', (tester) async {
+      await tester.pumpWidget(
+        MaterialApp(
+          // we need the SingleChildScrollView to have a scroll controller
+          // available to the StickyHeader widget
+          home: SingleChildScrollView(
+            child: StickyHeader(
+              header: Container(height: 50.0),
+              content: Container(height: 200.0),
+            ),
+          ),
+        ),
+      );
+      // check that the height is 250.0 (50.0 for the header + 200.0 for the content)
+      expect(tester.getSize(find.byType(StickyHeader)).height, 250.0);
+    });
+
+    testWidgets('has correct size when set to true', (tester) async {
+      await tester.pumpWidget(
+        MaterialApp(
+          // we need the SingleChildScrollView to have a scroll controller
+          // available to the StickyHeader widget
+          home: SingleChildScrollView(
+            child: StickyHeader(
+              overlapHeaders: true,
+              header: Container(height: 50.0),
+              content: Container(height: 200.0),
+            ),
+          ),
+        ),
+      );
+
+      // check that the height is 200.0 (200.0 for the content because the header is overlapping it)
+      expect(tester.getSize(find.byType(StickyHeader)).height, 200.0);
+    });
+  });
+  group('StickyHeaderBuilder', () {
+    testWidgets('defaults to not overlapping headers', (tester) async {
+      await tester.pumpWidget(
+        MaterialApp(
+          home: SingleChildScrollView(
+            child: StickyHeaderBuilder(
+              builder: (context, stuckAmount) {
+                return Container(height: 50.0);
+              },
+              content: Container(height: 200.0),
+            ),
+          ),
+        ),
+      );
+      expect(tester.getSize(find.byType(StickyHeader)).height, 250.0);
+    });
+
+    testWidgets('overlaps headers when set to true', (tester) async {
+      await tester.pumpWidget(
+        MaterialApp(
+          home: SingleChildScrollView(
+            child: StickyHeaderBuilder(
+              builder: (context, stuckAmount) {
+                return Container(height: 50.0);
+              },
+              content: Container(height: 200.0),
+              overlapHeaders: true,
+            ),
+          ),
+        ),
+      );
+      expect(tester.getSize(find.byType(StickyHeader)).height, 200.0);
+    });
+
+    testWidgets('calls builder with correct stuck amount', (tester) async {
+      double? capturedStuckAmount;
+      await tester.pumpWidget(
+        MaterialApp(
+          home: SingleChildScrollView(
+            child: StickyHeaderBuilder(
+              builder: (context, stuckAmount) {
+                capturedStuckAmount = stuckAmount;
+                return Container(height: 50.0);
+              },
+              content: Container(height: 200.0),
+            ),
+          ),
+        ),
+      );
+      expect(capturedStuckAmount, 0.0);
+    });
+  });
+}