Add parser tests (#4)

* test: add test for parsing multiple stylesheets
* test: add test for parsing css with expressions

src/test/parse_test.ts

@@ -1,4 +1,4 @@
-import {Root, Rule, Declaration} from 'postcss';
+import {Root, Rule, Declaration, Comment} from 'postcss';
 import {assert} from 'chai';
 import {createTestAst} from './util.js';
 
@@ -59,4 +59,51 @@ describe('parse', () => {
     assert.equal(rule.type, 'rule');
     assert.equal(colour.type, 'decl');
   });
+
+  it('should parse multiple stylesheets', () => {
+    const {source, ast} = createTestAst(`
+      css\`
+        .foo { color: hotpink; }
+      \`;
+
+      css\`.bar: { background: lime; }\`;
+    `);
+    assert.equal(ast.nodes.length, 2);
+    const root1 = ast.nodes[0] as Root;
+    const root2 = ast.nodes[1] as Root;
+
+    assert.equal(root1.type, 'root');
+    assert.equal(root1.raws.codeBefore, '\n      css`');
+    assert.equal(root1.raws.codeAfter, undefined);
+    assert.equal(root1.parent, ast);
+    assert.equal(root2.type, 'root');
+    assert.equal(root2.raws.codeBefore, '`;\n\n      css`');
+    assert.equal(root2.raws.codeAfter, '`;\n    ');
+    assert.equal(root2.parent, ast);
+
+    assert.deepEqual(ast.source!.start, {
+      line: 1,
+      column: 1,
+      offset: 0
+    });
+    assert.equal(ast.source!.input.css, source);
+  });
+
+  it('should parse CSS containing an expression', () => {
+    const {source, ast} = createTestAst(`
+      css\`
+        .foo { $\{expr}color: hotpink; }
+      \`;
+    `);
+    const root = ast.nodes[0] as Root;
+    const rule = root.nodes[0] as Rule;
+    const placeholder = rule.nodes[0] as Comment;
+    const colour = rule.nodes[1] as Declaration;
+    assert.equal(ast.type, 'document');
+    assert.equal(root.type, 'root');
+    assert.equal(rule.type, 'rule');
+    assert.equal(placeholder.type, 'comment');
+    assert.equal(colour.type, 'decl');
+    assert.equal(ast.source!.input.css, source);
+  });
 });