Add test for encounteredNonImportNodes logic (#614)

Co-authored-by: Romain Menke <11521496+romainmenke@users.noreply.github.com>

Author: RyanZim

test/fixtures/imports/layer-after-content.css

@@ -0,0 +1,4 @@
+html {
+  box-sizing: border-box;
+}
+@layer overrides;

test/fixtures/layer-after-content.css

@@ -0,0 +1,4 @@
+@import "layer-after-content.css";
+.foo {
+  color: red;
+}

test/fixtures/layer-after-content.expected.css

@@ -0,0 +1,7 @@
+html {
+  box-sizing: border-box;
+}
+@layer overrides;
+.foo {
+  color: red;
+}

test/layer.js

@@ -58,6 +58,12 @@ test(
   "layer-statement-with-conditions",
 )
 
+test(
+  "should preserve the order of layer statements that follow other CSS",
+  checkFixture,
+  "layer-after-content",
+)
+
 test(
   "should preserve the order of layer statements that follow layer blocks",
   checkFixture,