diff --git a/src/builtin/tags/assign.ts b/src/builtin/tags/assign.ts
index 2eaa2f5777..520b76893f 100644
--- a/src/builtin/tags/assign.ts
+++ b/src/builtin/tags/assign.ts
@@ -14,10 +14,9 @@ export default {
     this.key = match[1]
     this.value = match[2]
   },
-  render: function (scope: Scope) {
+  render: async function (scope: Scope) {
     const ctx = new AssignScope()
-    ctx[this.key] = this.liquid.evalValue(this.value, scope)
+    ctx[this.key] = await this.liquid.evalValue(this.value, scope)
     scope.push(ctx)
-    return Promise.resolve('')
   }
 } as ITagImplOptions
diff --git a/src/builtin/tags/case.ts b/src/builtin/tags/case.ts
index 6310527d39..198a7a13a6 100644
--- a/src/builtin/tags/case.ts
+++ b/src/builtin/tags/case.ts
@@ -30,11 +30,11 @@ export default {
     stream.start()
   },
 
-  render: function (scope: Scope) {
+  render: async function (scope: Scope) {
     for (let i = 0; i < this.cases.length; i++) {
       const branch = this.cases[i]
-      const val = evalExp(branch.val, scope)
-      const cond = evalExp(this.cond, scope)
+      const val = await evalExp(branch.val, scope)
+      const cond = await evalExp(this.cond, scope)
       if (val === cond) {
         return this.liquid.renderer.renderTemplates(branch.templates, scope)
       }
diff --git a/src/builtin/tags/cycle.ts b/src/builtin/tags/cycle.ts
index 56df884405..5dd7ba0c86 100644
--- a/src/builtin/tags/cycle.ts
+++ b/src/builtin/tags/cycle.ts
@@ -24,8 +24,8 @@ export default <ITagImplOptions>{
     assert(this.candidates.length, `empty candidates: ${tagToken.raw}`)
   },
 
-  render: function (scope: Scope) {
-    const group = evalValue(this.group, scope)
+  render: async function (scope: Scope) {
+    const group = await evalValue(this.group, scope)
     const fingerprint = `cycle:${group}:` + this.candidates.join(',')
     const groups = scope.groups
     let idx = groups[fingerprint]
diff --git a/src/builtin/tags/for.ts b/src/builtin/tags/for.ts
index 60f5af1e91..d53fedfeac 100644
--- a/src/builtin/tags/for.ts
+++ b/src/builtin/tags/for.ts
@@ -42,7 +42,7 @@ export default <ITagImplOptions>{
     stream.start()
   },
   render: async function (scope: Scope, hash: Hash) {
-    let collection = evalExp(this.collection, scope)
+    let collection = await evalExp(this.collection, scope)
 
     if (!isArray(collection)) {
       if (isString(collection) && collection.length > 0) {
diff --git a/src/builtin/tags/if.ts b/src/builtin/tags/if.ts
index 49effaf17f..1f4a4beeca 100644
--- a/src/builtin/tags/if.ts
+++ b/src/builtin/tags/if.ts
@@ -33,9 +33,9 @@ export default {
     stream.start()
   },
 
-  render: function (scope: Scope) {
+  render: async function (scope: Scope) {
     for (const branch of this.branches) {
-      const cond = evalExp(branch.cond, scope)
+      const cond = await evalExp(branch.cond, scope)
       if (isTruthy(cond)) {
         return this.liquid.renderer.renderTemplates(branch.templates, scope)
       }
diff --git a/src/builtin/tags/include.ts b/src/builtin/tags/include.ts
index fcac6f7aff..7eb4d7a951 100644
--- a/src/builtin/tags/include.ts
+++ b/src/builtin/tags/include.ts
@@ -34,7 +34,7 @@ export default <ITagImplOptions>{
         const template = this.value.slice(1, -1)
         filepath = await this.liquid.parseAndRender(template, scope.getAll(), scope.opts)
       } else {
-        filepath = evalValue(this.value, scope)
+        filepath = await evalValue(this.value, scope)
       }
     } else {
       filepath = this.staticValue
@@ -47,7 +47,7 @@ export default <ITagImplOptions>{
     scope.blocks = {}
     scope.blockMode = BlockMode.OUTPUT
     if (this.with) {
-      hash[filepath] = evalValue(this.with, scope)
+      hash[filepath] = await evalValue(this.with, scope)
     }
     const templates = await this.liquid.getTemplate(filepath, scope.opts)
     scope.push(hash)
diff --git a/src/builtin/tags/layout.ts b/src/builtin/tags/layout.ts
index 4b650cfbdd..592dec4485 100644
--- a/src/builtin/tags/layout.ts
+++ b/src/builtin/tags/layout.ts
@@ -26,7 +26,7 @@ export default {
   },
   render: async function (scope: Scope, hash: Hash) {
     const layout = scope.opts.dynamicPartials
-      ? evalValue(this.layout, scope)
+      ? await evalValue(this.layout, scope)
       : this.staticLayout
     assert(layout, `cannot apply layout with empty filename`)
 
diff --git a/src/builtin/tags/tablerow.ts b/src/builtin/tags/tablerow.ts
index 2562b83748..4cf16dc9dc 100644
--- a/src/builtin/tags/tablerow.ts
+++ b/src/builtin/tags/tablerow.ts
@@ -36,7 +36,7 @@ export default {
   },
 
   render: async function (scope: Scope, hash: Hash) {
-    let collection = evalExp(this.collection, scope) || []
+    let collection = await evalExp(this.collection, scope) || []
     const offset = hash.offset || 0
     const limit = (hash.limit === undefined) ? collection.length : hash.limit
 
diff --git a/src/builtin/tags/unless.ts b/src/builtin/tags/unless.ts
index c5c45491df..a2a6687c28 100644
--- a/src/builtin/tags/unless.ts
+++ b/src/builtin/tags/unless.ts
@@ -25,8 +25,8 @@ export default {
     stream.start()
   },
 
-  render: function (scope: Scope) {
-    const cond = evalExp(this.cond, scope)
+  render: async function (scope: Scope) {
+    const cond = await evalExp(this.cond, scope)
     return isFalsy(cond)
       ? this.liquid.renderer.renderTemplates(this.templates, scope)
       : this.liquid.renderer.renderTemplates(this.elseTemplates, scope)
diff --git a/src/drop/drop.ts b/src/drop/drop.ts
index 82c86d1bfa..7015e39a1d 100644
--- a/src/drop/drop.ts
+++ b/src/drop/drop.ts
@@ -3,7 +3,7 @@ export abstract class Drop {
     return undefined
   }
 
-  liquidMethodMissing (key: string): string | undefined {
+  liquidMethodMissing (key: string): Promise<string | undefined> | string | undefined {
     return undefined
   }
 }
diff --git a/src/render/syntax.ts b/src/render/syntax.ts
index b4041b457f..3f9d0f36be 100644
--- a/src/render/syntax.ts
+++ b/src/render/syntax.ts
@@ -48,7 +48,7 @@ const binaryOperators: {[key: string]: (lhs: any, rhs: any) => boolean} = {
   'or': (l: any, r: any) => isTruthy(l) || isTruthy(r)
 }
 
-export function parseExp (exp: string, scope: Scope): any {
+export async function parseExp (exp: string, scope: Scope): Promise<any> {
   assert(scope, 'unable to parseExp: scope undefined')
   const operatorREs = lexical.operators
   let match
@@ -56,28 +56,28 @@ export function parseExp (exp: string, scope: Scope): any {
     const operatorRE = operatorREs[i]
     const expRE = new RegExp(`^(${lexical.quoteBalanced.source})(${operatorRE.source})(${lexical.quoteBalanced.source})$`)
     if ((match = exp.match(expRE))) {
-      const l = parseExp(match[1], scope)
+      const l = await parseExp(match[1], scope)
       const op = binaryOperators[match[2].trim()]
-      const r = parseExp(match[3], scope)
+      const r = await parseExp(match[3], scope)
       return op(l, r)
     }
   }
 
   if ((match = exp.match(lexical.rangeLine))) {
-    const low = evalValue(match[1], scope)
-    const high = evalValue(match[2], scope)
-    return range(low, high + 1)
+    const low = await evalValue(match[1], scope)
+    const high = await evalValue(match[2], scope)
+    return range(+low, +high + 1)
   }
 
   return parseValue(exp, scope)
 }
 
-export function evalExp (str: string, scope: Scope): any {
-  const value = parseExp(str, scope)
+export async function evalExp (str: string, scope: Scope): Promise<any> {
+  const value = await parseExp(str, scope)
   return value instanceof Drop ? value.valueOf() : value
 }
 
-function parseValue (str: string | undefined, scope: Scope): any {
+async function parseValue (str: string | undefined, scope: Scope): Promise<any> {
   if (!str) return null
   str = str.trim()
 
@@ -91,8 +91,8 @@ function parseValue (str: string | undefined, scope: Scope): any {
   return scope.get(str)
 }
 
-export function evalValue (str: string | undefined, scope: Scope): any {
-  const value = parseValue(str, scope)
+export async function evalValue (str: string | undefined, scope: Scope) {
+  const value = await parseValue(str, scope)
   return value instanceof Drop ? value.valueOf() : value
 }
 
diff --git a/src/scope/context.ts b/src/scope/context.ts
new file mode 100644
index 0000000000..7789e0ad42
--- /dev/null
+++ b/src/scope/context.ts
@@ -0,0 +1,10 @@
+import { Drop } from '../drop/drop'
+
+type PlainObject = {
+  [key: string]: any
+  liquid_method_missing?: (key: string) => any // eslint-disable-line
+  to_liquid?: () => any // eslint-disable-line
+  toLiquid?: () => any  // eslint-disable-line
+}
+
+export type Context = PlainObject | Drop
\ No newline at end of file
diff --git a/src/scope/scope.ts b/src/scope/scope.ts
index 91a37e1eda..1c00f31426 100644
--- a/src/scope/scope.ts
+++ b/src/scope/scope.ts
@@ -4,13 +4,7 @@ import { __assign } from 'tslib'
 import assert from '../util/assert'
 import { NormalizedFullOptions, applyDefault } from '../liquid-options'
 import BlockMode from './block-mode'
-
-export type Context = {
-  [key: string]: any
-  liquid_method_missing?: (key: string) => any // eslint-disable-line
-  to_liquid?: () => any // eslint-disable-line
-  toLiquid?: () => any  // eslint-disable-line
-}
+import { Context } from './context'
 
 export default class Scope {
   opts: NormalizedFullOptions
@@ -25,19 +19,19 @@ export default class Scope {
   getAll () {
     return this.contexts.reduce((ctx, val) => __assign(ctx, val), {})
   }
-  get (path: string): any {
-    const paths = this.propertyAccessSeq(path)
-    const scope = this.findContextFor(paths[0]) || _.last(this.contexts)
-    return paths.reduce((value, key) => {
-      const val = this.readProperty(value, key)
-      if (_.isNil(val) && this.opts.strictVariables) {
-        throw new TypeError(`undefined variable: ${key}`)
+  async get (path: string) {
+    const paths = await this.propertyAccessSeq(path)
+    let ctx = this.findContextFor(paths[0]) || _.last(this.contexts)
+    for (let path of paths) {
+      ctx = this.readProperty(ctx, path)
+      if (_.isNil(ctx) && this.opts.strictVariables) {
+        throw new TypeError(`undefined variable: ${path}`)
       }
-      return val
-    }, scope)
+    }
+    return ctx
   }
-  set (path: string, v: any): void {
-    const paths = this.propertyAccessSeq(path)
+  async set (path: string, v: any) {
+    const paths = await this.propertyAccessSeq(path)
     let scope = this.findContextFor(paths[0]) || _.last(this.contexts)
     paths.some((key, i) => {
       if (!_.isObject(scope)) {
@@ -99,7 +93,7 @@ export default class Scope {
    * accessSeq("foo['b]r']")      // ['foo', 'b]r']
    * accessSeq("foo[bar.coo]")    // ['foo', 'bar'], for bar.coo == 'bar'
    */
-  propertyAccessSeq (str: string) {
+  async propertyAccessSeq (str: string) {
     str = String(str)
     const seq: string[] = []
     let name = ''
@@ -122,7 +116,7 @@ export default class Scope {
             assert(j !== -1, `unbalanced []: ${str}`)
             name = str.slice(i + 1, j)
             if (!/^[+-]?\d+$/.test(name)) { // foo[bar] vs. foo[1]
-              name = String(this.get(name))
+              name = String(await this.get(name))
             }
             push()
             i = j + 1
@@ -152,9 +146,9 @@ export default class Scope {
 }
 
 function readSize (obj: Context) {
-  if (!_.isNil(obj.size)) return obj.size
+  if (!_.isNil(obj['size'])) return obj['size']
   if (_.isArray(obj) || _.isString(obj)) return obj.length
-  return obj.size
+  return obj['size']
 }
 
 function matchRightBracket (str: string, begin: number) {
diff --git a/src/template/filter/filter.ts b/src/template/filter/filter.ts
index a06c4f6587..e931415c81 100644
--- a/src/template/filter/filter.ts
+++ b/src/template/filter/filter.ts
@@ -19,9 +19,13 @@ export class Filter {
     this.impl = impl || (x => x)
     this.args = args
   }
-  render (value: any, scope: Scope): any {
-    const args = this.args.map(arg => isArray(arg) ? [arg[0], evalValue(arg[1], scope)] : evalValue(arg, scope))
-    return this.impl.apply(null, [value, ...args])
+  async render (value: any, scope: Scope) {
+    const argv: any[] = []
+    for(let arg of this.args) {
+      if (isArray(arg)) argv.push([arg[0], await evalValue(arg[1], scope)])
+      else argv.push(await evalValue(arg, scope))
+    }
+    return this.impl.apply(null, [value, ...argv])
   }
   static register (name: string, filter: FilterImpl) {
     Filter.impls[name] = filter
diff --git a/src/template/tag/hash.ts b/src/template/tag/hash.ts
index 66a587e940..a95d29aae4 100644
--- a/src/template/tag/hash.ts
+++ b/src/template/tag/hash.ts
@@ -10,13 +10,15 @@ import Scope from '../../scope/scope'
  */
 export default class Hash {
   [key: string]: any
-  constructor (markup: string, scope: Scope) {
+  static async create (markup: string, scope: Scope) {
+    const instance = new Hash()
     let match
     hashCapture.lastIndex = 0
     while ((match = hashCapture.exec(markup))) {
       const k = match[1]
       const v = match[2]
-      this[k] = evalValue(v, scope)
+      instance[k] = await evalValue(v, scope)
     }
+    return instance
   }
 }
diff --git a/src/template/tag/tag.ts b/src/template/tag/tag.ts
index f5f8908d28..e6e79870f0 100644
--- a/src/template/tag/tag.ts
+++ b/src/template/tag/tag.ts
@@ -28,7 +28,7 @@ export default class Tag extends Template<TagToken> implements ITemplate {
     }
   }
   async render (scope: Scope) {
-    const hash = new Hash(this.token.args, scope)
+    const hash = await Hash.create(this.token.args, scope)
     const impl = this.impl
     if (typeof impl.render !== 'function') {
       return ''
diff --git a/src/template/value.ts b/src/template/value.ts
index a590e4631b..23418136d7 100644
--- a/src/template/value.ts
+++ b/src/template/value.ts
@@ -47,10 +47,12 @@ export default class Value {
     }
     this.filters.push(new Filter(name, args, this.strictFilters))
   }
-  value (scope: Scope) {
-    return this.filters.reduce(
-      (prev, filter) => filter.render(prev, scope),
-      evalExp(this.initial, scope))
+  async value (scope: Scope) {
+    let val = await evalExp(this.initial, scope)
+    for (let filter of this.filters) {
+      val = await filter.render(val, scope)
+    }
+    return val
   }
   static tokenize (str: string): Array<'|' | ',' | ':' | string> {
     const tokens = []
diff --git a/test/e2e/eval-value.ts b/test/e2e/eval-value.ts
index cba0f539c9..4727cd0cbb 100644
--- a/test/e2e/eval-value.ts
+++ b/test/e2e/eval-value.ts
@@ -5,7 +5,7 @@ describe('.evalValue()', function () {
   var engine: Liquid
   beforeEach(() => { engine = new Liquid() })
 
-  it('should throw when scope undefined', function () {
-    expect(() => engine.evalValue('{{"foo"}}', null as any)).to.throw(/scope undefined/)
+  it('should throw when scope undefined', async function () {
+    return expect(engine.evalValue('{{"foo"}}', null as any)).to.be.rejectedWith(/scope undefined/)
   })
 })
diff --git a/test/integration/builtin/filters/array.ts b/test/integration/builtin/filters/array.ts
index a062e073ef..5d2c2ba5a0 100644
--- a/test/integration/builtin/filters/array.ts
+++ b/test/integration/builtin/filters/array.ts
@@ -33,9 +33,9 @@ describe('filters/array', function () {
                 ' | split: ", " %}{{ my_array | size }}',
       '4')
     })
-    it('should also be used with dot notation - string',
+    it('should be respected with <string>.size notation',
       () => test('{% assign my_string = "Ground control to Major Tom." %}{{ my_string.size }}', '28'))
-    it('should also be used with dot notation - array',
+    it('should be respected with <array>.size notation',
       () => test('{% assign my_array = "apples, oranges, peaches, plums" | split: ", " %}{{ my_array.size }}', '4'))
   })
   describe('slice', function () {
diff --git a/test/integration/builtin/tags/for.ts b/test/integration/builtin/tags/for.ts
index a5b3921cd3..2861915d9b 100644
--- a/test/integration/builtin/tags/for.ts
+++ b/test/integration/builtin/tags/for.ts
@@ -1,7 +1,7 @@
 import Liquid from '../../../../src/liquid'
 import { expect, use } from 'chai'
 import * as chaiAsPromised from 'chai-as-promised'
-import { Context } from '../../../../src/scope/scope'
+import { Context } from '../../../../src/scope/context'
 
 use(chaiAsPromised)
 
diff --git a/test/integration/drop/drop.ts b/test/integration/drop/drop.ts
index 8510bf8e83..3ac1674b81 100644
--- a/test/integration/drop/drop.ts
+++ b/test/integration/drop/drop.ts
@@ -8,7 +8,7 @@ describe('drop/drop', function () {
   class CustomDrop extends Liquid.Types.Drop {
     name: string = 'NAME'
     getName () {
-      return 'GETNAME'
+      return 'GET NAME'
     }
   }
   class CustomDropWithMethodMissing extends CustomDrop {
@@ -16,9 +16,18 @@ describe('drop/drop', function () {
       return key.toUpperCase()
     }
   }
+  class PromiseDrop extends Liquid.Types.Drop {
+    name = Promise.resolve('NAME')
+    async getName () {
+      return 'GET NAME'
+    }
+    async liquidMethodMissing (key: string) {
+      return key.toUpperCase()
+    }
+  }
   it('should call corresponding method', async function () {
     const html = await liquid.parseAndRender(`{{obj.getName}}`, { obj: new CustomDrop() })
-    expect(html).to.equal('GETNAME')
+    expect(html).to.equal('GET NAME')
   })
   it('should read corresponding property', async function () {
     const html = await liquid.parseAndRender(`{{obj.name}}`, { obj: new CustomDrop() })
@@ -32,4 +41,16 @@ describe('drop/drop', function () {
     const html = await liquid.parseAndRender(`{{obj.foo}}`, { obj: new CustomDropWithMethodMissing() })
     expect(html).to.equal('FOO')
   })
+  it('should call corresponding promise method', async function () {
+    const html = await liquid.parseAndRender(`{{obj.getName}}`, { obj: new PromiseDrop() })
+    expect(html).to.equal('GET NAME')
+  })
+  it('should read corresponding promise property', async function () {
+    const html = await liquid.parseAndRender(`{{obj.name}}`, { obj: new PromiseDrop() })
+    expect(html).to.equal('NAME')
+  })
+  it('should support promise returned by liquidMethodMissing', async function () {
+    const html = await liquid.parseAndRender(`{{obj.foo}}`, { obj: new PromiseDrop() })
+    expect(html).to.equal('FOO')
+  })
 })
diff --git a/test/unit/render/syntax.ts b/test/unit/render/syntax.ts
index 5621c3e0c8..486bf1869f 100644
--- a/test/unit/render/syntax.ts
+++ b/test/unit/render/syntax.ts
@@ -18,35 +18,35 @@ describe('render/syntax', function () {
   })
 
   describe('.evalValue()', function () {
-    it('should eval boolean literal', function () {
-      expect(evalValue('true', scope)).to.equal(true)
-      expect(evalValue('TrUE', scope)).to.equal(undefined)
-      expect(evalValue('false', scope)).to.equal(false)
+    it('should eval boolean literal', async function () {
+      expect(await evalValue('true', scope)).to.equal(true)
+      expect(await evalValue('TrUE', scope)).to.equal(undefined)
+      expect(await evalValue('false', scope)).to.equal(false)
     })
-    it('should eval number literal', function () {
-      expect(evalValue('2.3', scope)).to.equal(2.3)
-      expect(evalValue('.32', scope)).to.equal(0.32)
-      expect(evalValue('-23.', scope)).to.equal(-23)
-      expect(evalValue('23', scope)).to.equal(23)
+    it('should eval number literal', async function () {
+      expect(await evalValue('2.3', scope)).to.equal(2.3)
+      expect(await evalValue('.32', scope)).to.equal(0.32)
+      expect(await evalValue('-23.', scope)).to.equal(-23)
+      expect(await evalValue('23', scope)).to.equal(23)
     })
-    it('should eval string literal', function () {
-      expect(evalValue('"ab\'c"', scope)).to.equal("ab'c")
-      expect(evalValue("'ab\"c'", scope)).to.equal('ab"c')
+    it('should eval string literal', async function () {
+      expect(await evalValue('"ab\'c"', scope)).to.equal("ab'c")
+      expect(await evalValue("'ab\"c'", scope)).to.equal('ab"c')
     })
-    it('should eval nil literal', function () {
-      expect(evalValue('nil', scope)).to.be.null
+    it('should eval nil literal', async function () {
+      expect(await evalValue('nil', scope)).to.be.null
     })
-    it('should eval null literal', function () {
-      expect(evalValue('null', scope)).to.be.null
+    it('should eval null literal', async function () {
+      expect(await evalValue('null', scope)).to.be.null
     })
-    it('should eval scope variables', function () {
-      expect(evalValue('one', scope)).to.equal(1)
-      expect(evalValue('has_value?', scope)).to.equal(true)
-      expect(evalValue('x', scope)).to.equal('XXX')
+    it('should eval scope variables', async function () {
+      expect(await evalValue('one', scope)).to.equal(1)
+      expect(await evalValue('has_value?', scope)).to.equal(true)
+      expect(await evalValue('x', scope)).to.equal('XXX')
     })
   })
 
-  describe('.isTruthy()', function () {
+  describe('.isTruthy()', async function () {
     // Spec: https://shopify.github.io/liquid/basics/truthy-and-falsy/
     expect(isTruthy(true)).to.be.true
     expect(isTruthy(false)).to.be.false
@@ -61,44 +61,42 @@ describe('render/syntax', function () {
   })
 
   describe('.evalExp()', function () {
-    it('should throw when scope undefined', function () {
-      expect(function () {
-        (evalExp as any)('')
-      }).to.throw(/scope undefined/)
+    it('should throw when scope undefined', async function () {
+      return expect((evalExp as any)('')).to.be.rejectedWith(/scope undefined/)
     })
 
-    it('should eval simple expression', function () {
-      expect(evalExp('1<2', scope)).to.equal(true)
-      expect(evalExp('2<=2', scope)).to.equal(true)
-      expect(evalExp('one<=two', scope)).to.equal(true)
-      expect(evalExp('x contains "x"', scope)).to.equal(false)
-      expect(evalExp('x contains "X"', scope)).to.equal(true)
-      expect(evalExp('1 contains "x"', scope)).to.equal(false)
-      expect(evalExp('y contains "x"', scope)).to.equal(false)
-      expect(evalExp('z contains "x"', scope)).to.equal(false)
-      expect(evalExp('(1..5) contains 3', scope)).to.equal(true)
-      expect(evalExp('(1..5) contains 6', scope)).to.equal(false)
-      expect(evalExp('"<=" == "<="', scope)).to.equal(true)
+    it('should eval simple expression', async function () {
+      expect(await evalExp('1<2', scope)).to.equal(true)
+      expect(await evalExp('2<=2', scope)).to.equal(true)
+      expect(await evalExp('one<=two', scope)).to.equal(true)
+      expect(await evalExp('x contains "x"', scope)).to.equal(false)
+      expect(await evalExp('x contains "X"', scope)).to.equal(true)
+      expect(await evalExp('1 contains "x"', scope)).to.equal(false)
+      expect(await evalExp('y contains "x"', scope)).to.equal(false)
+      expect(await evalExp('z contains "x"', scope)).to.equal(false)
+      expect(await evalExp('(1..5) contains 3', scope)).to.equal(true)
+      expect(await evalExp('(1..5) contains 6', scope)).to.equal(false)
+      expect(await evalExp('"<=" == "<="', scope)).to.equal(true)
     })
 
     describe('complex expression', function () {
-      it('should support value or value', function () {
-        expect(evalExp('false or true', scope)).to.equal(true)
+      it('should support value or value', async function () {
+        expect(await evalExp('false or true', scope)).to.equal(true)
       })
-      it('should support < and contains', function () {
-        expect(evalExp('1<2 and x contains "x"', scope)).to.equal(false)
+      it('should support < and contains', async function () {
+        expect(await evalExp('1<2 and x contains "x"', scope)).to.equal(false)
       })
-      it('should support < or contains', function () {
-        expect(evalExp('1<2 or x contains "x"', scope)).to.equal(true)
+      it('should support < or contains', async function () {
+        expect(await evalExp('1<2 or x contains "x"', scope)).to.equal(true)
       })
-      it('should support value and !=', function () {
-        expect(evalExp('empty and empty != ""', scope)).to.equal(false)
+      it('should support value and !=', async function () {
+        expect(await evalExp('empty and empty != ""', scope)).to.equal(false)
       })
     })
 
-    it('should eval range expression', function () {
-      expect(evalExp('(2..4)', scope)).to.deep.equal([2, 3, 4])
-      expect(evalExp('(two..4)', scope)).to.deep.equal([2, 3, 4])
+    it('should eval range expression', async function () {
+      expect(await evalExp('(2..4)', scope)).to.deep.equal([2, 3, 4])
+      expect(await evalExp('(two..4)', scope)).to.deep.equal([2, 3, 4])
     })
   })
 })
diff --git a/test/unit/scope/scope.ts b/test/unit/scope/scope.ts
index dccd4781d1..70cc2ee2d9 100644
--- a/test/unit/scope/scope.ts
+++ b/test/unit/scope/scope.ts
@@ -1,5 +1,6 @@
 import * as chai from 'chai'
-import Scope, { Context } from '../../../src/scope/scope'
+import Scope from '../../../src/scope/scope'
+import { Context } from '../../../src/scope/context'
 
 const expect = chai.expect
 
@@ -20,168 +21,156 @@ describe('scope', function () {
   })
 
   describe('#propertyAccessSeq()', function () {
-    it('should handle dot syntax', function () {
-      expect(scope.propertyAccessSeq('foo.bar'))
+    it('should handle dot syntax', async function () {
+      expect(await scope.propertyAccessSeq('foo.bar'))
         .to.deep.equal(['foo', 'bar'])
     })
-    it('should handle [<String>] syntax', function () {
-      expect(scope.propertyAccessSeq('foo["bar"]'))
+    it('should handle [<String>] syntax', async function () {
+      expect(await scope.propertyAccessSeq('foo["bar"]'))
         .to.deep.equal(['foo', 'bar'])
     })
-    it('should handle [<Identifier>] syntax', function () {
-      expect(scope.propertyAccessSeq('foo[foo]'))
+    it('should handle [<Identifier>] syntax', async function () {
+      expect(await scope.propertyAccessSeq('foo[foo]'))
         .to.deep.equal(['foo', 'zoo'])
     })
-    it('should handle nested access 1', function () {
-      expect(scope.propertyAccessSeq('foo[bar.zoo]'))
+    it('should handle nested access 1', async function () {
+      expect(await scope.propertyAccessSeq('foo[bar.zoo]'))
         .to.deep.equal(['foo', 'coo'])
     })
-    it('should handle nested access 2', function () {
-      expect(scope.propertyAccessSeq('foo[bar["zoo"]]'))
+    it('should handle nested access 2', async function () {
+      expect(await scope.propertyAccessSeq('foo[bar["zoo"]]'))
         .to.deep.equal(['foo', 'coo'])
     })
-    it('should handle nested access 3', function () {
-      expect(scope.propertyAccessSeq('bar["foo"].zoo'))
+    it('should handle nested access 3', async function () {
+      expect(await scope.propertyAccessSeq('bar["foo"].zoo'))
         .to.deep.equal(['bar', 'foo', 'zoo'])
     })
-    it('should handle nested access 4', function () {
-      expect(scope.propertyAccessSeq('foo[0].bar'))
+    it('should handle nested access 4', async function () {
+      expect(await scope.propertyAccessSeq('foo[0].bar'))
         .to.deep.equal(['foo', '0', 'bar'])
     })
-    it('should handle nested access 5', function () {
-      expect(scope.propertyAccessSeq('foo[one].bar'))
+    it('should handle nested access 5', async function () {
+      expect(await scope.propertyAccessSeq('foo[one].bar'))
         .to.deep.equal(['foo', '1', 'bar'])
     })
-    it('should handle nested access 6', function () {
-      expect(scope.propertyAccessSeq('foo[two].bar'))
+    it('should handle nested access 6', async function () {
+      expect(await scope.propertyAccessSeq('foo[two].bar'))
         .to.deep.equal(['foo', 'undefined', 'bar'])
     })
   })
 
   describe('#get()', function () {
-    it('should get direct property', function () {
-      expect(scope.get('foo')).equal('zoo')
+    it('should get direct property', async function () {
+      expect(await await scope.get('foo')).equal('zoo')
     })
 
-    it('undefined property should yield undefined', function () {
-      function fn () {
-        scope.get('notdefined')
-      }
-      expect(fn).to.not.throw()
-      expect(scope.get('notdefined')).to.equal(undefined)
-      expect(scope.get(false as any)).to.equal(undefined)
+    it('undefined property should yield undefined', async function () {
+      expect(scope.get('notdefined')).to.be.rejected
+      expect(await scope.get('notdefined')).to.equal(undefined)
+      expect(await scope.get(false as any)).to.equal(undefined)
     })
 
-    it('should throw for invalid path', function () {
-      function fn () {
-        scope.get('')
-      }
-      expect(fn).to.throw('invalid path:""')
+    it('should throw for invalid path', async function () {
+      expect(scope.get('')).to.be.rejectedWith('invalid path:""')
     })
 
-    it('should throw when [] unbalanced', function () {
-      expect(function () {
-        scope.get('foo[bar')
-      }).to.throw(/unbalanced \[\]/)
+    it('should throw when [] unbalanced', async function () {
+      expect(scope.get('foo[bar')).to.be.rejectedWith(/unbalanced \[\]/)
     })
 
-    it('should throw when "" unbalanced', function () {
-      expect(function () {
-        scope.get('foo["bar]')
-      }).to.throw(/unbalanced "/)
+    it('should throw when "" unbalanced', async function () {
+      expect(scope.get('foo["bar]')).to.be.rejectedWith(/unbalanced "/)
     })
 
-    it("should throw when '' unbalanced", function () {
-      expect(function () {
-        scope.get("foo['bar]")
-      }).to.throw(/unbalanced '/)
+    it("should throw when '' unbalanced", async function () {
+      expect(scope.get("foo['bar]")).to.be.rejectedWith(/unbalanced '/)
     })
 
-    it('should respect to to_liquid', function () {
+    it('should respect to to_liquid', async function () {
       const scope = new Scope({ foo: {
         to_liquid: () => ({ bar: 'BAR' }),
         bar: 'bar'
       } })
-      expect(scope.get('foo.bar')).to.equal('BAR')
+      expect(await scope.get('foo.bar')).to.equal('BAR')
     })
 
-    it('should respect to toLiquid', function () {
+    it('should respect to toLiquid', async function () {
       const scope = new Scope({ foo: {
         toLiquid: () => ({ bar: 'BAR' }),
         bar: 'bar'
       } })
-      expect(scope.get('foo.bar')).to.equal('BAR')
+      expect(await scope.get('foo.bar')).to.equal('BAR')
     })
 
-    it('should access child property via dot syntax', function () {
-      expect(scope.get('bar.zoo')).to.equal('coo')
-      expect(scope.get('bar.arr')).to.deep.equal(['a', 'b'])
+    it('should access child property via dot syntax', async function () {
+      expect(await scope.get('bar.zoo')).to.equal('coo')
+      expect(await scope.get('bar.arr')).to.deep.equal(['a', 'b'])
     })
 
-    it('should access child property via [<String>] syntax', function () {
-      expect(scope.get('bar["zoo"]')).to.equal('coo')
+    it('should access child property via [<String>] syntax', async function () {
+      expect(await scope.get('bar["zoo"]')).to.equal('coo')
     })
 
-    it('should access child property via [<Number>] syntax', function () {
-      expect(scope.get('bar.arr[0]')).to.equal('a')
+    it('should access child property via [<Number>] syntax', async function () {
+      expect(await scope.get('bar.arr[0]')).to.equal('a')
     })
 
-    it('should access child property via [<Identifier>] syntax', function () {
-      expect(scope.get('bar[foo]')).to.equal('coo')
+    it('should access child property via [<Identifier>] syntax', async function () {
+      expect(await scope.get('bar[foo]')).to.equal('coo')
     })
 
-    it('should return undefined when not exist', function () {
-      expect(scope.get('foo.foo.foo')).to.be.undefined
+    it('should return undefined when not exist', async function () {
+      expect(await scope.get('foo.foo.foo')).to.be.undefined
     })
-    it('should return string length as size', function () {
-      expect(scope.get('foo.size')).to.equal(3)
+    it('should return string length as size', async function () {
+      expect(await scope.get('foo.size')).to.equal(3)
     })
-    it('should return array length as size', function () {
-      expect(scope.get('bar.arr.size')).to.equal(2)
+    it('should return array length as size', async function () {
+      expect(await scope.get('bar.arr.size')).to.equal(2)
     })
-    it('should return size property if exists', function () {
-      expect(scope.get('zoo.size')).to.equal(4)
+    it('should return size property if exists', async function () {
+      expect(await scope.get('zoo.size')).to.equal(4)
     })
-    it('should return undefined if do not have size and length', function () {
-      expect(scope.get('one.size')).to.equal(undefined)
+    it('should return undefined if do not have size and length', async function () {
+      expect(await scope.get('one.size')).to.equal(undefined)
     })
   })
 
   describe('#set', function () {
-    it('should set nested value', function () {
-      scope.set('posts', {
+    it('should set nested value', async function () {
+      await scope.set('posts', {
         'first': {
           'name': 'A Nice Day'
         }
       })
-      scope.set('category', {
+      await scope.set('category', {
         'diary': ['first']
       })
-      expect(scope.get('posts[category.diary[0]].name'), 'A Nice Day')
+      expect(await scope.get('posts[category.diary[0]].name'), 'A Nice Day')
     })
 
-    it('should create parent if needed', function () {
-      scope.set('a.b.c.d', 'COO')
-      expect(scope.get('a.b.c.d')).to.equal('COO')
+    it('should create parent if needed', async function () {
+      await scope.set('a.b.c.d', 'COO')
+      expect(await scope.get('a.b.c.d')).to.equal('COO')
     })
-    it('should keep other properties of parent', function () {
+    it('should keep other properties of parent', async function () {
       scope.push({ obj: { foo: 'FOO' } })
-      scope.set('obj.bar', 'BAR')
-      expect(scope.get('obj.foo')).to.equal('FOO')
+      await scope.set('obj.bar', 'BAR')
+      expect(await scope.get('obj.foo')).to.equal('FOO')
     })
-    it('should abort if property cannot be set', function () {
+    it('should abort if property cannot be set', async function () {
       scope.push({ obj: { foo: 'FOO' } })
-      scope.set('obj.foo.bar', 'BAR')
-      expect(scope.get('obj.foo')).to.equal('FOO')
+      await scope.set('obj.foo.bar', 'BAR')
+      expect(await scope.get('obj.foo')).to.equal('FOO')
     })
-    it("should set parents' corresponding value", function () {
+    it("should set parents' corresponding value", async function () {
       scope.push({})
-      scope.set('foo', 'bar')
+      await scope.set('foo', 'bar')
       scope.pop()
-      expect(scope.get('foo')).to.equal('bar')
+      expect(await scope.get('foo')).to.equal('bar')
     })
   })
-  describe('strictVariables', function () {
+  describe('strictVariables', async function () {
     let scope: Scope
     beforeEach(function () {
       scope = new Scope(ctx, {
@@ -189,66 +178,57 @@ describe('scope', function () {
       } as any)
     })
     it('should throw when variable not defined', function () {
-      function fn () {
-        scope.get('notdefined')
-      }
-      expect(fn).to.throw(/undefined variable: notdefined/)
+      return expect(scope.get('notdefined')).to.be.rejectedWith(/undefined variable: notdefined/)
     })
-    it('should throw when deep variable not exist', function () {
-      scope.set('foo', 'FOO')
-      function fn () {
-        scope.get('foo.bar.not.defined')
-      }
-      expect(fn).to.throw(/undefined variable: bar/)
+    it('should throw when deep variable not exist', async function () {
+      await scope.set('foo', 'FOO')
+      return expect(scope.get('foo.bar.not.defined')).to.be.rejectedWith(/undefined variable: bar/)
     })
-    it('should throw when itself not defined', function () {
-      scope.set('foo', 'bar')
-      function fn () {
-        scope.get('foo.BAR')
-      }
-      expect(fn).to.throw(/undefined variable: BAR/)
+    it('should throw when itself not defined', async function () {
+      await scope.set('foo', 'bar')
+      return expect(scope.get('foo.BAR')).to.be.rejectedWith(/undefined variable: BAR/)
     })
-    it('should find variable in parent scope', function () {
-      scope.set('foo', 'foo')
+    it('should find variable in parent scope', async function () {
+      await scope.set('foo', 'foo')
       scope.push({
         'bar': 'bar'
       })
-      expect(scope.get('foo')).to.equal('foo')
+      expect(await scope.get('foo')).to.equal('foo')
     })
   })
 
   describe('.getAll()', function () {
-    it('should get all properties when arguments empty', function () {
-      expect(scope.getAll()).deep.equal(ctx)
+    it('should get all properties when arguments empty', async function () {
+      expect(await scope.getAll()).deep.equal(ctx)
     })
   })
 
   describe('.push()', function () {
-    it('should push scope', function () {
-      scope.set('bar', 'bar')
+    it('should push scope', async function () {
+      await scope.set('bar', 'bar')
       scope.push({
         foo: 'foo'
       })
-      expect(scope.get('foo')).to.equal('foo')
-      expect(scope.get('bar')).to.equal('bar')
+      expect(await scope.get('foo')).to.equal('foo')
+      expect(await scope.get('bar')).to.equal('bar')
     })
-    it('should hide deep properties by push', function () {
-      scope.set('bar', { bar: 'bar' })
+    it('should hide deep properties by push', async function () {
+      await scope.set('bar', { bar: 'bar' })
       scope.push({ bar: { foo: 'foo' } })
-      expect(scope.get('bar.foo')).to.equal('foo')
-      expect(scope.get('bar.bar')).to.equal(undefined)
+      expect(await scope.get('bar.foo')).to.equal('foo')
+      expect(await scope.get('bar.bar')).to.equal(undefined)
     })
   })
   describe('.pop()', function () {
-    it('should pop scope', function () {
+    it('should pop scope', async function () {
       scope.push({
         foo: 'foo'
       })
       scope.pop()
-      expect(scope.get('foo')).to.equal('zoo')
+      expect(await scope.get('foo')).to.equal('zoo')
     })
   })
-  it('should pop specified scope', function () {
+  it('should pop specified scope', async function () {
     const scope1 = {
       foo: 'foo'
     }
@@ -257,11 +237,11 @@ describe('scope', function () {
     }
     scope.push(scope1)
     scope.push(scope2)
-    expect(scope.get('foo')).to.equal('foo')
-    expect(scope.get('bar')).to.equal('bar')
+    expect(await scope.get('foo')).to.equal('foo')
+    expect(await scope.get('bar')).to.equal('bar')
     scope.pop(scope1)
-    expect(scope.get('foo')).to.equal('zoo')
-    expect(scope.get('bar')).to.equal('bar')
+    expect(await scope.get('foo')).to.equal('zoo')
+    expect(await scope.get('bar')).to.equal('bar')
   })
   it('should throw when specified scope not found', function () {
     const scope1 = {
diff --git a/test/unit/template/filter/filter.ts b/test/unit/template/filter/filter.ts
index 86dab239a1..7293313bc1 100644
--- a/test/unit/template/filter/filter.ts
+++ b/test/unit/template/filter/filter.ts
@@ -13,34 +13,34 @@ describe('filter', function () {
     Filter.clear()
     scope = new Scope()
   })
-  it('should create default filter if not registered', function () {
+  it('should create default filter if not registered', async function () {
     const result = new Filter('foo', [], false)
     expect(result.name).to.equal('foo')
   })
 
-  it('should render input if filter not registered', function () {
-    expect(new Filter('undefined', [], false).render('foo', scope)).to.equal('foo')
+  it('should render input if filter not registered', async function () {
+    expect(await new Filter('undefined', [], false).render('foo', scope)).to.equal('foo')
   })
 
-  it('should call filter impl with corrct arguments', function () {
+  it('should call filter impl with corrct arguments', async function () {
     const spy = sinon.spy()
     Filter.register('foo', spy)
-    new Filter('foo', ['33'], false).render('foo', scope)
+    await new Filter('foo', ['33'], false).render('foo', scope)
     expect(spy).to.have.been.calledWith('foo', 33)
   })
-  it('should render a simple filter', function () {
+  it('should render a simple filter', async function () {
     Filter.register('upcase', x => x.toUpperCase())
-    expect(new Filter('upcase', [], false).render('foo', scope)).to.equal('FOO')
+    expect(await new Filter('upcase', [], false).render('foo', scope)).to.equal('FOO')
   })
 
-  it('should render filters with argument', function () {
+  it('should render filters with argument', async function () {
     Filter.register('add', (a, b) => a + b)
-    expect(new Filter('add', ['2'], false).render(3, scope)).to.equal(5)
+    expect(await new Filter('add', ['2'], false).render(3, scope)).to.equal(5)
   })
 
-  it('should render filters with multiple arguments', function () {
+  it('should render filters with multiple arguments', async function () {
     Filter.register('add', (a, b, c) => a + b + c)
-    expect(new Filter('add', ['2', '"c"'], false).render(3, scope)).to.equal('5c')
+    expect(await new Filter('add', ['2', '"c"'], false).render(3, scope)).to.equal('5c')
   })
 
   it('should not throw when filter name illegal', function () {
diff --git a/test/unit/template/value.ts b/test/unit/template/value.ts
index 2753dff797..7608325793 100644
--- a/test/unit/template/value.ts
+++ b/test/unit/template/value.ts
@@ -99,7 +99,7 @@ describe('Value', function () {
   })
 
   describe('#value()', function () {
-    it('should call chained filters correctly', function () {
+    it('should call chained filters correctly', async function () {
       const date = sinon.stub().returns('y')
       const time = sinon.spy()
       Filter.register('date', date)
@@ -108,7 +108,7 @@ describe('Value', function () {
       const scope = new Scope({
         foo: { bar: 'bar' }
       })
-      tpl.value(scope)
+      await tpl.value(scope)
       expect(date).to.have.been.calledWith('bar', 'b')
       expect(time).to.have.been.calledWith('y', 2)
     })