diff --git a/packages/compiler-core/src/parse.ts b/packages/compiler-core/src/parse.ts
index ee70ecfa..0b0cf83f 100644
--- a/packages/compiler-core/src/parse.ts
+++ b/packages/compiler-core/src/parse.ts
@@ -141,7 +141,7 @@ function parseChildren(
   const nodes: TemplateChildNode[] = []
 
   while (!isEnd(context, mode, ancestors)) {
-    __DEV__ && assert(context.source.length > 0)
+    __TEST__ && assert(context.source.length > 0)
     const s = context.source
     let node: TemplateChildNode | TemplateChildNode[] | undefined = undefined
 
@@ -286,16 +286,16 @@ function parseCDATA(
   context: ParserContext,
   ancestors: ElementNode[]
 ): TemplateChildNode[] {
-  __DEV__ &&
+  __TEST__ &&
     assert(last(ancestors) == null || last(ancestors)!.ns !== Namespaces.HTML)
-  __DEV__ && assert(startsWith(context.source, '<![CDATA['))
+  __TEST__ && assert(startsWith(context.source, '<![CDATA['))
 
   advanceBy(context, 9)
   const nodes = parseChildren(context, TextModes.CDATA, ancestors)
   if (context.source.length === 0) {
     emitError(context, ErrorCodes.EOF_IN_CDATA)
   } else {
-    __DEV__ && assert(startsWith(context.source, ']]>'))
+    __TEST__ && assert(startsWith(context.source, ']]>'))
     advanceBy(context, 3)
   }
 
@@ -303,7 +303,7 @@ function parseCDATA(
 }
 
 function parseComment(context: ParserContext): CommentNode {
-  __DEV__ && assert(startsWith(context.source, '<!--'))
+  __TEST__ && assert(startsWith(context.source, '<!--'))
 
   const start = getCursor(context)
   let content: string
@@ -345,7 +345,7 @@ function parseComment(context: ParserContext): CommentNode {
 }
 
 function parseBogusComment(context: ParserContext): CommentNode | undefined {
-  __DEV__ && assert(/^<(?:[\!\?]|\/[^a-z>])/i.test(context.source))
+  __TEST__ && assert(/^<(?:[\!\?]|\/[^a-z>])/i.test(context.source))
 
   const start = getCursor(context)
   const contentStart = context.source[1] === '?' ? 1 : 2
@@ -371,7 +371,7 @@ function parseElement(
   context: ParserContext,
   ancestors: ElementNode[]
 ): ElementNode | undefined {
-  __DEV__ && assert(/^<[a-z]/i.test(context.source))
+  __TEST__ && assert(/^<[a-z]/i.test(context.source))
 
   // Start tag.
   const wasInPre = context.inPre
@@ -425,8 +425,8 @@ function parseTag(
   type: TagType,
   parent: ElementNode | undefined
 ): ElementNode {
-  __DEV__ && assert(/^<\/?[a-z]/i.test(context.source))
-  __DEV__ &&
+  __TEST__ && assert(/^<\/?[a-z]/i.test(context.source))
+  __TEST__ &&
     assert(
       type === (startsWith(context.source, '</') ? TagType.End : TagType.Start)
     )
@@ -538,7 +538,7 @@ function parseAttribute(
   context: ParserContext,
   nameSet: Set<string>
 ): AttributeNode | DirectiveNode {
-  __DEV__ && assert(/^[^\t\r\n\f />]/.test(context.source))
+  __TEST__ && assert(/^[^\t\r\n\f />]/.test(context.source))
 
   // Name.
   const start = getCursor(context)
@@ -725,7 +725,7 @@ function parseInterpolation(
   mode: TextModes
 ): InterpolationNode | undefined {
   const [open, close] = context.options.delimiters
-  __DEV__ && assert(startsWith(context.source, open))
+  __TEST__ && assert(startsWith(context.source, open))
 
   const closeIndex = context.source.indexOf(close, open.length)
   if (closeIndex === -1) {
@@ -765,7 +765,7 @@ function parseInterpolation(
 }
 
 function parseText(context: ParserContext, mode: TextModes): TextNode {
-  __DEV__ && assert(context.source.length > 0)
+  __TEST__ && assert(context.source.length > 0)
 
   const [open] = context.options.delimiters
   // TODO could probably use some perf optimization
@@ -777,7 +777,7 @@ function parseText(context: ParserContext, mode: TextModes): TextNode {
       context.source.length
     ].filter(n => n !== -1)
   )
-  __DEV__ && assert(endIndex > 0)
+  __TEST__ && assert(endIndex > 0)
 
   const start = getCursor(context)
   const content = parseTextData(context, endIndex, mode)
@@ -951,7 +951,7 @@ function startsWith(source: string, searchString: string): boolean {
 
 function advanceBy(context: ParserContext, numberOfCharacters: number): void {
   const { source } = context
-  __DEV__ && assert(numberOfCharacters <= source.length)
+  __TEST__ && assert(numberOfCharacters <= source.length)
   advancePositionWithMutation(context, source, numberOfCharacters)
   context.source = source.slice(numberOfCharacters)
 }
diff --git a/packages/compiler-core/src/transforms/transformElement.ts b/packages/compiler-core/src/transforms/transformElement.ts
index 909b460f..e7935a63 100644
--- a/packages/compiler-core/src/transforms/transformElement.ts
+++ b/packages/compiler-core/src/transforms/transformElement.ts
@@ -51,7 +51,7 @@ export const transformElement: NodeTransform = (node, context) => {
   }
   // perform the work on exit, after all child expressions have been
   // processed and merged.
-  return () => {
+  return function postTransformElement() {
     const { tag, tagType, props } = node
     const isPortal = tag === 'portal' || tag === 'Portal'
     const isSuspense = tag === 'suspense' || tag === 'Suspense'
@@ -113,7 +113,7 @@ export const transformElement: NodeTransform = (node, context) => {
         node,
         context,
         // skip reserved "is" prop <component is>
-        node.props.filter(p => p !== isProp)
+        isProp ? node.props.filter(p => p !== isProp) : node.props
       )
       patchFlag = propsBuildResult.patchFlag
       dynamicPropNames = propsBuildResult.dynamicPropNames
@@ -177,9 +177,7 @@ export const transformElement: NodeTransform = (node, context) => {
         args.push(patchFlag + '')
       }
       if (dynamicPropNames && dynamicPropNames.length) {
-        args.push(
-          `[${dynamicPropNames.map(n => JSON.stringify(n)).join(`, `)}]`
-        )
+        args.push(stringifyDynamicPropNames(dynamicPropNames))
       }
     }
 
@@ -204,6 +202,15 @@ export const transformElement: NodeTransform = (node, context) => {
   }
 }
 
+function stringifyDynamicPropNames(props: string[]): string {
+  let propsNamesString = `[`
+  for (let i = 0, l = props.length; i < l; i++) {
+    propsNamesString += JSON.stringify(props[i])
+    if (i < l - 1) propsNamesString += ', '
+  }
+  return propsNamesString + `]`
+}
+
 export type PropsExpression = ObjectExpression | CallExpression | ExpressionNode
 
 export function buildProps(
@@ -410,7 +417,7 @@ export function buildProps(
 // - onXXX handlers / style: merge into array
 // - class: merge into single expression with concatenation
 function dedupeProperties(properties: Property[]): Property[] {
-  const knownProps: Record<string, Property> = {}
+  const knownProps: Map<string, Property> = new Map()
   const deduped: Property[] = []
   for (let i = 0; i < properties.length; i++) {
     const prop = properties[i]
@@ -420,7 +427,7 @@ function dedupeProperties(properties: Property[]): Property[] {
       continue
     }
     const name = prop.key.content
-    const existing = knownProps[name]
+    const existing = knownProps.get(name)
     if (existing) {
       if (
         name === 'style' ||
@@ -432,7 +439,7 @@ function dedupeProperties(properties: Property[]): Property[] {
       }
       // unexpected duplicate, should have emitted error during parse
     } else {
-      knownProps[name] = prop
+      knownProps.set(name, prop)
       deduped.push(prop)
     }
   }
diff --git a/packages/compiler-core/src/transforms/vSlot.ts b/packages/compiler-core/src/transforms/vSlot.ts
index bb432792..33506c84 100644
--- a/packages/compiler-core/src/transforms/vSlot.ts
+++ b/packages/compiler-core/src/transforms/vSlot.ts
@@ -208,7 +208,7 @@ export function buildSlots(
         // remove node
         children.splice(i, 1)
         i--
-        __DEV__ && assert(dynamicSlots.length > 0)
+        __TEST__ && assert(dynamicSlots.length > 0)
         // attach this slot to previous conditional
         let conditional = dynamicSlots[
           dynamicSlots.length - 1
diff --git a/packages/compiler-core/src/utils.ts b/packages/compiler-core/src/utils.ts
index 5b1a9ebc..aff8437e 100644
--- a/packages/compiler-core/src/utils.ts
+++ b/packages/compiler-core/src/utils.ts
@@ -77,7 +77,7 @@ export function getInnerRange(
   offset: number,
   length?: number
 ): SourceLocation {
-  __DEV__ && assert(offset <= loc.source.length)
+  __TEST__ && assert(offset <= loc.source.length)
   const source = loc.source.substr(offset, length)
   const newLoc: SourceLocation = {
     source,
@@ -86,7 +86,7 @@ export function getInnerRange(
   }
 
   if (length != null) {
-    __DEV__ && assert(offset + length <= loc.source.length)
+    __TEST__ && assert(offset + length <= loc.source.length)
     newLoc.end = advancePositionWithClone(
       loc.start,
       loc.source,