only replace components for changed segments

test/common/test.js

@@ -632,6 +632,33 @@ function run({ mode, basepath = '' }) {
 						assert.equal(html.indexOf('%sapper'), -1);
 					});
 			});
+
+			it('only recreates components when necessary', () => {
+				return nightmare
+					.goto(`${base}/foo/bar/baz`)
+					.init()
+					.evaluate(() => document.querySelector('#sapper').textContent)
+					.then(text => {
+						assert.deepEqual(text.split('\n').filter(Boolean), [
+							'x: foo 1',
+							'y: bar 1',
+							'z: baz 1'
+						]);
+
+						return nightmare.click(`a`)
+							.then(() => wait(100))
+							.then(() => {
+								return nightmare.evaluate(() => document.querySelector('#sapper').textContent);
+							});
+					})
+					.then(text => {
+						assert.deepEqual(text.split('\n').filter(Boolean), [
+							'x: foo 1',
+							'y: bar 1',
+							'z: qux 2'
+						]);
+					});
+			});
 		});
 
 		describe('headers', () => {