diff --git a/html/highlighter.ts b/html/highlighter.ts
index 67ae3ba..218981e 100644
--- a/html/highlighter.ts
+++ b/html/highlighter.ts
@@ -2,6 +2,7 @@ import { Palette } from "./highlighter/palette";
 import { Node, Position } from "./highlighter/node";
 import { State } from "./highlighter/state";
 import { Token, Type } from "./tokenizer/token";
+import { TODO, VERIFY, VERIFY_NOT_REACHED } from "../util/assertions.js";
 
 export class Highlighter {
     private state: State = State.Undefined;
@@ -28,7 +29,7 @@ export class Highlighter {
                 case Type.DOCTYPE: this.reconsumeIn(State.DOCTYPE); break;
                 case Type.Comment: this.reconsumeIn(State.Comment); break;
                 case Type.EndOfFile: this.finished = true; break;
-                default: throw new Error(`FIXME (Highlighter#spin, Unimplemented token type '${this.currentToken.type}')`);
+                default: TODO(`Highlighter#spin, Unimplemented token type '${this.currentToken.type}'`);
             }
 
             break;
@@ -39,7 +40,7 @@ export class Highlighter {
                     this.createNode({ position: { line: 0, character: 0 }, color: Palette.Plain, content: '' });
                     this.reconsumeIn(State.Plain);
                     break;
-                default: throw new Error('BeforePlain')
+                default: VERIFY_NOT_REACHED();
             }
 
             break;
@@ -159,7 +160,7 @@ export class Highlighter {
 
             this.state = State.Undefined;
             break;
-        default: throw new Error(`FIXME (Highlighter#iterate, Unimplemented state '${this.state}')`);
+        default: TODO(`Highlighter#iterate, Unimplemented state '${this.state}'`);
         }
     }
 
@@ -178,9 +179,7 @@ export class Highlighter {
     private consumeNextTokenOfType<T extends Type>(type: T): Token & { type: T } {
         this.currentToken = this.tokens[this.pointer];
 
-        console.assert(this.currentToken.type === type, {
-            message: `Highlighter#consumeNextOfType: Expected '${type}', got '${this.currentToken.type}' instead`
-        });
+        VERIFY(this.currentToken.type === type, `Highlighter#consumeNextOfType: Expected '${type}', got '${this.currentToken.type}' instead`);
 
         this.pointer++;
 
@@ -190,9 +189,8 @@ export class Highlighter {
     private consumeNextTokenOfEitherType<T extends Type, U extends Type>(a: T, b: U): Token & { type: T | U } {
         this.currentToken = this.tokens[this.pointer];
 
-        console.assert(this.currentToken.type === a || this.currentToken.type === b, {
-            message: `Highlighter#consumeNextTokenOfEitherType: Expected '${a}' or '${b}', got '${this.currentToken.type}' instead`
-        });
+        VERIFY(this.currentToken.type === a || this.currentToken.type === b,
+            `Highlighter#consumeNextTokenOfEitherType: Expected '${a}' or '${b}', got '${this.currentToken.type}' instead`);
 
         this.pointer++;
 
@@ -214,17 +212,14 @@ export class Highlighter {
     }
 
     private currentTokenOfType<T extends Type>(type: T): Token & { type: T } {
-        console.assert(this.currentToken.type === type, {
-            message: `Highlighter#currentTokenOfType: Expected '${type}', got '${this.currentToken.type}' instead`
-        });
+        VERIFY(this.currentToken.type === type, `Highlighter#currentTokenOfType: Expected '${type}', got '${this.currentToken.type}' instead`);
 
         return this.currentToken as Token & { type: T };
     }
 
     private currentTokenOfEitherType<T extends Type, U extends Type>(a: T, b: U): Token & { type: T | U } {
-        console.assert(this.currentToken.type === a || this.currentToken.type === b, {
-            message: `Highlighter#currentTokenOfEitherType: Expected '${a}' or '${b}', got '${this.currentToken.type}' instead`
-        });
+        VERIFY(this.currentToken.type === a || this.currentToken.type === b,
+            `Highlighter#currentTokenOfEitherType: Expected '${a}' or '${b}', got '${this.currentToken.type}' instead`);
 
         return this.currentToken as Token & { type: T };
     }
diff --git a/html/tokenizer.ts b/html/tokenizer.ts
index aec4c6d..0af5441 100644
--- a/html/tokenizer.ts
+++ b/html/tokenizer.ts
@@ -1,9 +1,9 @@
+import { TODO, VERIFY } from "../util/assertions.js";
 import { ParseError } from "./errors.js";
 import { entities } from "./tokenizer/entities.js";
 import { State } from "./tokenizer/state.js";
 import { AttributeList, Token, Type } from "./tokenizer/token.js";
 
-// FIXME: Replace console.assert calls will throwing errors
 export class Tokenizer {
     private state: State = State.Data;
     private returnState!: State;
@@ -510,7 +510,7 @@ export class Tokenizer {
 
             break;
         }
-        default: throw new Error(`FIXME (Tokenizer#iterate, Unimplemented state '${this.state}')`);
+        default: TODO(`Tokenizer#iterate, Unimplemented state '${this.state}'`);
         }
     }
 
@@ -581,9 +581,7 @@ export class Tokenizer {
         for (let i = 0; i < input.length; i++) {
             const consumed = this.consumeNext();
 
-            console.assert(consumed === input[i], {
-                message: `Tokenizer#consumeNextFew: Expected '${input[i]}' (${input} at ${i}), got ${consumed} instead`
-            });
+            VERIFY(consumed === input[i], `Tokenizer#consumeNextFew: Expected '${input[i]}' (${input} at ${i}), got ${consumed} instead`);
         }
     }
 
@@ -591,9 +589,8 @@ export class Tokenizer {
         for (let i = 0; i < input.length; i++) {
             const consumed = this.consumeNext()?.toLowerCase();
 
-            console.assert(consumed === input[i].toLowerCase(), {
-                message: `Tokenizer#consumeNextFewCaseInsensitive: Expected '${input[i].toLowerCase()}' (${input.toLowerCase()} at ${i}), got ${consumed} instead`
-            });
+            VERIFY(consumed === input[i].toLowerCase(),
+                `Tokenizer#consumeNextFewCaseInsensitive: Expected '${input[i].toLowerCase()}' (${input.toLowerCase()} at ${i}), got ${consumed} instead`);
         }
     }
 
@@ -602,33 +599,26 @@ export class Tokenizer {
     }
 
     private emitCurrentOfType(type: Type): void {
-        console.assert(this.currentToken.type === type, {
-            message: `Tokenizer#emitCurrentOfType: Expected '${type}', got '${this.currentToken.type}' instead`
-        });
+        VERIFY(this.currentToken.type === type, `Tokenizer#emitCurrentOfType: Expected '${type}', got '${this.currentToken.type}' instead`);
 
         this.tokens.push(this.currentToken);
     }
 
     private emitCurrentOfEitherType(a: Type, b: Type): void {
-        console.assert(this.currentToken.type === a || this.currentToken.type === b, {
-            message: `Tokenizer#emitCurrentOfEitherType: Expected '${a}' or '${b}', got '${this.currentToken.type}' instead`
-        });
+        VERIFY(this.currentToken.type === a || this.currentToken.type === b, `Tokenizer#emitCurrentOfEitherType: Expected '${a}' or '${b}', got '${this.currentToken.type}' instead`);
 
         this.tokens.push(this.currentToken);
     }
 
     private currentOfType<T extends Type>(type: T): Token & { type: T } {
-        console.assert(this.currentToken.type === type, {
-            message: `Tokenizer#currentOfType: Expected '${type}', got '${this.currentToken.type}' instead`
-        });
+        VERIFY(this.currentToken.type === type, `Tokenizer#currentOfType: Expected '${type}', got '${this.currentToken.type}' instead`);
 
         return this.currentToken as Token & { type: T };
     }
 
     private currentOfEitherType<T extends Type, U extends Type>(a: T, b: U): Token & { type: T | U } {
-        console.assert(this.currentToken.type === a || this.currentToken.type === b, {
-            message: `Tokenizer#currentOfEitherType: Expected '${a}' or '${b}', got '${this.currentToken.type}' instead`
-        });
+        VERIFY(this.currentToken.type === a || this.currentToken.type === b,
+            `Tokenizer#currentOfEitherType: Expected '${a}' or '${b}', got '${this.currentToken.type}' instead`);
 
         return this.currentToken as Token & { type: T };
     }