diff --git a/src/scope.ts b/src/scope.ts
index f8a4579..2dd9f28 100644
--- a/src/scope.ts
+++ b/src/scope.ts
@@ -30,6 +30,15 @@ export class Scope {
   has(name: string): boolean {
     return this.locals.has(name) || this.parent?.has(name) || false
   }
+
+  vars(): string[] {
+    const vars = new Set(this.parent?.vars())
+
+    for (const name of this.locals.keys())
+      vars.add(name)
+
+    return [...vars].sort()
+  }
 }
 
 
diff --git a/src/vm.ts b/src/vm.ts
index 24ea531..aae6be6 100644
--- a/src/vm.ts
+++ b/src/vm.ts
@@ -48,6 +48,14 @@ export class VM {
     }
   }
 
+  has(name: string): boolean {
+    return this.scope.has(name)
+  }
+
+  vars(): string[] {
+    return this.scope.vars()
+  }
+
   get(name: string) {
     return this.scope.get(name)
   }
diff --git a/tests/scope.test.ts b/tests/scope.test.ts
new file mode 100644
index 0000000..417e6e0
--- /dev/null
+++ b/tests/scope.test.ts
@@ -0,0 +1,243 @@
+import { test, expect } from "bun:test"
+import { Scope, toValue } from "#reef"
+
+test("Scope - create empty scope", () => {
+  const scope = new Scope()
+  expect(scope.parent).toBeUndefined()
+  expect(scope.locals.size).toBe(0)
+})
+
+test("Scope - create child scope with parent", () => {
+  const parent = new Scope()
+  const child = new Scope(parent)
+
+  expect(child.parent).toBe(parent)
+  expect(child.locals.size).toBe(0)
+})
+
+test("Scope - set and get variable in same scope", () => {
+  const scope = new Scope()
+  const value = toValue(42)
+
+  scope.set("x", value)
+  expect(scope.get("x")).toBe(value)
+})
+
+test("Scope - get returns undefined for non-existent variable", () => {
+  const scope = new Scope()
+  expect(scope.get("x")).toBeUndefined()
+})
+
+test("Scope - set updates existing variable in same scope", () => {
+  const scope = new Scope()
+
+  scope.set("x", toValue(10))
+  expect(scope.get("x")).toEqual({ type: "number", value: 10 })
+
+  scope.set("x", toValue(20))
+  expect(scope.get("x")).toEqual({ type: "number", value: 20 })
+})
+
+test("Scope - get searches parent scope", () => {
+  const parent = new Scope()
+  const child = new Scope(parent)
+
+  parent.set("x", toValue(42))
+  expect(child.get("x")).toEqual({ type: "number", value: 42 })
+})
+
+test("Scope - get searches multiple levels up", () => {
+  const grandparent = new Scope()
+  const parent = new Scope(grandparent)
+  const child = new Scope(parent)
+
+  grandparent.set("x", toValue(100))
+  expect(child.get("x")).toEqual({ type: "number", value: 100 })
+})
+
+test("Scope - child updates parent variable when it exists (no shadowing)", () => {
+  const parent = new Scope()
+  const child = new Scope(parent)
+
+  parent.set("x", toValue(10))
+  child.set("x", toValue(20))
+
+  // set() updates parent's variable, not shadow it
+  expect(parent.get("x")).toEqual({ type: "number", value: 20 })
+  expect(child.get("x")).toEqual({ type: "number", value: 20 })
+  expect(child.locals.has("x")).toBe(false)
+})
+
+test("Scope - set updates parent scope variable when it exists", () => {
+  const parent = new Scope()
+  const child = new Scope(parent)
+
+  parent.set("x", toValue(10))
+  child.set("x", toValue(20))
+
+  // Should update parent's variable, not create new local one
+  expect(parent.get("x")).toEqual({ type: "number", value: 20 })
+  expect(child.get("x")).toEqual({ type: "number", value: 20 })
+  expect(child.locals.has("x")).toBe(false)
+})
+
+test("Scope - set creates new local variable when not found in parent", () => {
+  const parent = new Scope()
+  const child = new Scope(parent)
+
+  parent.set("x", toValue(10))
+  child.set("y", toValue(20))
+
+  expect(parent.get("x")).toEqual({ type: "number", value: 10 })
+  expect(parent.get("y")).toBeUndefined()
+  expect(child.get("x")).toEqual({ type: "number", value: 10 })
+  expect(child.get("y")).toEqual({ type: "number", value: 20 })
+  expect(child.locals.has("y")).toBe(true)
+})
+
+test("Scope - has returns true for variable in current scope", () => {
+  const scope = new Scope()
+  scope.set("x", toValue(42))
+
+  expect(scope.has("x")).toBe(true)
+  expect(scope.has("y")).toBe(false)
+})
+
+test("Scope - has returns true for variable in parent scope", () => {
+  const parent = new Scope()
+  const child = new Scope(parent)
+
+  parent.set("x", toValue(42))
+
+  expect(child.has("x")).toBe(true)
+  expect(child.has("y")).toBe(false)
+})
+
+test("Scope - has searches multiple levels up", () => {
+  const grandparent = new Scope()
+  const parent = new Scope(grandparent)
+  const child = new Scope(parent)
+
+  grandparent.set("x", toValue(100))
+
+  expect(child.has("x")).toBe(true)
+  expect(parent.has("x")).toBe(true)
+  expect(grandparent.has("x")).toBe(true)
+})
+
+test("Scope.vars() - returns empty array for empty scope", () => {
+  const scope = new Scope()
+  expect(scope.vars()).toEqual([])
+})
+
+test("Scope.vars() - returns single variable from current scope", () => {
+  const scope = new Scope()
+  scope.set("x", toValue(42))
+
+  expect(scope.vars()).toEqual(["x"])
+})
+
+test("Scope.vars() - returns multiple variables from current scope", () => {
+  const scope = new Scope()
+  scope.set("x", toValue(1))
+  scope.set("y", toValue(2))
+  scope.set("z", toValue(3))
+
+  const vars = scope.vars()
+  expect(vars.length).toBe(3)
+  expect(vars).toContain("x")
+  expect(vars).toContain("y")
+  expect(vars).toContain("z")
+})
+
+test("Scope.vars() - includes variables from parent scope", () => {
+  const parent = new Scope()
+  const child = new Scope(parent)
+
+  parent.set("x", toValue(1))
+  child.set("y", toValue(2))
+
+  const vars = child.vars()
+  expect(vars.length).toBe(2)
+  expect(vars).toContain("x")
+  expect(vars).toContain("y")
+})
+
+test("Scope.vars() - includes variables from multiple parent scopes", () => {
+  const grandparent = new Scope()
+  const parent = new Scope(grandparent)
+  const child = new Scope(parent)
+
+  grandparent.set("x", toValue(1))
+  parent.set("y", toValue(2))
+  child.set("z", toValue(3))
+
+  const vars = child.vars()
+  expect(vars.length).toBe(3)
+  expect(vars).toContain("x")
+  expect(vars).toContain("y")
+  expect(vars).toContain("z")
+})
+
+test("Scope.vars() - no duplicates when child updates parent variable", () => {
+  const parent = new Scope()
+  const child = new Scope(parent)
+
+  parent.set("x", toValue(10))
+  child.set("x", toValue(20))  // Updates parent, doesn't create local
+
+  // Only one "x" since child doesn't have its own local x
+  const vars = child.vars()
+  expect(vars).toEqual(["x"])
+})
+
+test("Scope.vars() - can't have duplicates if manually set in locals", () => {
+  const parent = new Scope()
+  const child = new Scope(parent)
+
+  parent.set("x", toValue(10))
+  child.locals.set("x", toValue(20))
+  const vars = child.vars()
+  expect(vars).toEqual(["x"])
+
+  expect(child.get("x")).toEqual({ type: "number", value: 20 })
+  expect(parent.get("x")).toEqual({ type: "number", value: 10 })
+})
+
+test("Scope.vars() - handles deep scope chains", () => {
+  let scope = new Scope()
+
+  // Create a deep chain: level0 -> level1 -> ... -> level5
+  for (let i = 0; i < 5; i++) {
+    scope.set(`var${i}`, toValue(i))
+    scope = new Scope(scope)
+  }
+
+  // Final scope should have all variables from the chain
+  const vars = scope.vars()
+  expect(vars.length).toBe(5)
+  expect(vars).toContain("var0")
+  expect(vars).toContain("var1")
+  expect(vars).toContain("var2")
+  expect(vars).toContain("var3")
+  expect(vars).toContain("var4")
+})
+
+test("Scope - can store and retrieve functions", () => {
+  const scope = new Scope()
+
+  const fnValue = {
+    type: 'function' as const,
+    value: '<function>' as const,
+    params: ['x'],
+    defaults: {},
+    body: 0,
+    variadic: false,
+    named: false,
+    parentScope: scope
+  }
+
+  scope.set("myFunc", fnValue)
+  expect(scope.get("myFunc")).toBe(fnValue)
+  expect(scope.get("myFunc")?.type).toBe("function")
+})