diff --git a/src/index.spec.ts b/src/index.spec.ts
deleted file mode 100644
index 5726046..0000000
--- a/src/index.spec.ts
+++ /dev/null
@@ -1,31 +0,0 @@
-import { expect, describe, it } from 'vitest'
-
-import { parse } from './index.js'
-
-describe('specification of CEL', () => {
-  describe('addition', () => {
-    it('should parse addition', () => {
-      const expr = '1 + 1'
-
-      const result = parse(expr)
-
-      expect(result).toBe(2)
-    })
-
-    it('should parse addition with multiple terms', () => {
-      const expr = '1 + 1 + 1'
-
-      const result = parse(expr)
-
-      expect(result).toBe(3)
-    })
-
-    it('should parse addition with multiple terms with different signs', () => {
-      const expr = '1 + 1 - 1'
-
-      const result = parse(expr)
-
-      expect(result).toBe(1)
-    })
-  })
-})
diff --git a/src/spec/atomic-expression.spec.ts b/src/spec/atomic-expression.spec.ts
new file mode 100644
index 0000000..f25e761
--- /dev/null
+++ b/src/spec/atomic-expression.spec.ts
@@ -0,0 +1,13 @@
+import { expect, describe, it } from 'vitest'
+
+import { parse } from '..'
+
+describe('atomic expressions', () => {
+  it('should parse a number', () => {
+    const expr = '1'
+
+    const result = parse(expr)
+
+    expect(result).toBe(1)
+  })
+})