diff --git a/.github/workflows/docs.yml b/.github/workflows/docs.yml
index 561d1c2a..cc38fbae 100644
--- a/.github/workflows/docs.yml
+++ b/.github/workflows/docs.yml
@@ -4,24 +4,27 @@ on:
   push:
     branches:
       - main
+
 permissions:
   contents: write
 
 jobs:
   deploy_pages:
     runs-on: ubuntu-latest
-
     steps:
     - name: Checkout 🛎️
       uses: actions/checkout@v3
+
     - uses: actions/setup-node@v3
       with:
         node-version: '18'
         cache: 'pnpm'
+
     - uses: pnpm/action-setup@v2
-        name: Install pnpm
-        with:
-          version: 8
+      name: Install pnpm
+      with:
+        version: 8
+
     - run: |
         pnpm install
         pnpm docs
diff --git a/jest.config.ts b/jest.config.ts
index 0af24189..ade69b28 100644
--- a/jest.config.ts
+++ b/jest.config.ts
@@ -1,4 +1,4 @@
-import { type JestConfigWithTsJest } from 'ts-jest';
+import type { JestConfigWithTsJest } from 'ts-jest';
 
 export default <JestConfigWithTsJest>{
 	transform: { '^.+\\.ts$': ['ts-jest', { useESM: true }] },
diff --git a/pkg/fs/lexer.test.ts b/pkg/fs/lexer.test.ts
index 00588dfb..59e15979 100644
--- a/pkg/fs/lexer.test.ts
+++ b/pkg/fs/lexer.test.ts
@@ -3,7 +3,7 @@ import { ThenI, SaveThe, IntoTheFile } from './tokens';
 
 import { Identifier } from '@slangroom/shared/tokens';
 
-test('that lexing works', async () => {
+test('lexing works', async () => {
 	// Given I have a contract with filesystem statements in it
 	const contract = `Rule unknown ignore
 Given I have a 'string' named 'stringToWrite'
diff --git a/pkg/fs/parser.ts b/pkg/fs/parser.ts
index a4ca2bbf..32e0492e 100644
--- a/pkg/fs/parser.ts
+++ b/pkg/fs/parser.ts
@@ -1,7 +1,7 @@
 import { IntoTheFile, SaveThe, ThenI, vocab } from './tokens';
 import { lex } from './lexer';
 
-import { CstParser, IToken } from '@slangroom/deps/chevrotain';
+import { CstParser, type IToken } from '@slangroom/deps/chevrotain';
 import { Identifier } from '@slangroom/shared/tokens';
 import { ZenroomParams } from '@slangroom/shared/zenroom';
 
@@ -19,7 +19,7 @@ class Parser extends CstParser {
 		this.performSelfAnalysis();
 	}
 
-	public fileOverrideStatement = this.RULE('fileOverrideStatement', () => {
+	fileOverrideStatement = this.RULE('fileOverrideStatement', () => {
 		this.CONSUME(ThenI);
 		this.CONSUME(SaveThe);
 		this.CONSUME(Identifier, { LABEL: 'content' });
diff --git a/pkg/fs/tokens.ts b/pkg/fs/tokens.ts
index 4d174654..f4292de7 100644
--- a/pkg/fs/tokens.ts
+++ b/pkg/fs/tokens.ts
@@ -18,7 +18,8 @@ export const SaveThe = createToken({
 	pattern: /save the/,
 });
 
-/** * The "into the file" statement, used to indicate the file to which to
+/**
+ * The "into the file" statement, used to indicate the file to which to
  * write.
  */
 export const IntoTheFile = createToken({
diff --git a/pkg/fs/visitor.test.ts b/pkg/fs/visitor.test.ts
index 9e767e0b..9c964f2a 100644
--- a/pkg/fs/visitor.test.ts
+++ b/pkg/fs/visitor.test.ts
@@ -1,6 +1,6 @@
 import { visit } from './visitor';
 
-test('that', async () => {
+test('ast is correct', async () => {
 	// Given I have a contract with filesystem statements in it
 	const contract = `Rule unknown ignore
 Given I have a 'string' named 'stringToWrite'
@@ -8,9 +8,18 @@ and I have a 'string' named 'nameOfTheFile'
 
 Then I save the 'stringToWrite' into the file 'nameOfTheFile'
 `;
-	await visit(contract, {
-		data: { stringToWrite: 'hello world', nameOfTheFile: 'hello-world.txt' },
-	});
-
-	expect(true).toStrictEqual(true);
+	// When I generate ast of the contract
+	const data = {
+		stringToWrite: 'hello world',
+		nameOfTheFile: 'hello-world.txt',
+	};
+	const ast = await visit(contract, { data: data });
+	// Then the content must be "stringToWrite"
+	expect(ast.content).toStrictEqual('stringToWrite');
+	// and the filename must be "nameOfTheFile"
+	expect(ast.filename).toStrictEqual('nameOfTheFile');
+	// and the value indexed by the content in data must be "hello world"
+	expect(data[ast.content as 'stringToWrite']).toStrictEqual('hello world');
+	// and the value indexed by the filename in data must be "hello-world.txt"
+	expect(data[ast.filename as 'nameOfTheFile']).toStrictEqual('hello-world.txt');
 });
diff --git a/pkg/fs/visitor.ts b/pkg/fs/visitor.ts
index a5e5ee7e..b4401cdb 100644
--- a/pkg/fs/visitor.ts
+++ b/pkg/fs/visitor.ts
@@ -1,7 +1,7 @@
 import { BaseFsVisitor, parse, type FileOverrideStatementCtx } from './parser';
 
-import { type ZenroomParams } from '@slangroom/shared';
-import { type CstNode } from '@slangroom/deps/chevrotain';
+import type { ZenroomParams } from '@slangroom/shared';
+import type { CstNode } from '@slangroom/deps/chevrotain';
 
 export type FileOverrideStatement = {
 	content: string;
@@ -23,8 +23,8 @@ class Visitor extends BaseFsVisitor {
 		const content = ctx.content[0].image;
 		const filename = ctx.filename[0].image;
 		return {
-			content: content,
-			filename: filename,
+			content: content.slice(1, -1),
+			filename: filename.slice(1, -1),
 		};
 	}
 }
diff --git a/pkg/ignored/index.test.ts b/pkg/ignored/index.test.ts
index efc9e996..e4f7d7f2 100644
--- a/pkg/ignored/index.test.ts
+++ b/pkg/ignored/index.test.ts
@@ -1,6 +1,6 @@
 import { getIgnoredStatements } from './index';
 
-test("that zenroom ignores statements it doesn't know in general", async () => {
+test("zenroom ignores statements it doesn't know in general", async () => {
 	// Given I have a contract with a general rule unknown statemets in it
 	const uknowns = [
 		'When I test the rule with a statement that does not exist 1',
@@ -21,7 +21,7 @@ Then print the data
 	expect(result).toStrictEqual(uknowns);
 });
 
-test("that zenroom doesn't ignore ecdh but ignores restroom statements", async () => {
+test("zenroom doesn't ignore ecdh but ignores restroom statements", async () => {
 	// Given I have a contract with ecdh and restroom statements
 	const contract = `# Always use 'Rule caller restroom-mw' when using Restroom
 Rule caller restroom-mw
diff --git a/pkg/ignored/index.ts b/pkg/ignored/index.ts
index 2f6f4d94..a6d9169c 100644
--- a/pkg/ignored/index.ts
+++ b/pkg/ignored/index.ts
@@ -1,6 +1,6 @@
 import { vocab } from './tokens';
 
-import { type ZenroomParams, zencodeExec } from '@slangroom/shared';
+import { zencodeExec, type ZenroomParams } from '@slangroom/shared';
 import { Lexer } from '@slangroom/deps/chevrotain';
 
 const IgnoredLexer = new Lexer(vocab);
diff --git a/pkg/ignored/tokens.ts b/pkg/ignored/tokens.ts
index fa3f9386..24f78512 100644
--- a/pkg/ignored/tokens.ts
+++ b/pkg/ignored/tokens.ts
@@ -4,15 +4,14 @@ import { createToken, CustomPatternMatcherFunc } from '@slangroom/deps/chevrotai
 /*
  * Prevent regex-ast annoing warnings
  * https://github.com/Chevrotain/chevrotain/issues/1670#issuecomment-1001673472
- * */
+ */
 const wrap = (regex: RegExp): CustomPatternMatcherFunc => {
-    return (text: string, offset: number): RegExpExecArray | null => {
-        const re = new RegExp(regex, 'y');
-        re.lastIndex = offset
-        return re.exec(text)
-    }
-}
-
+	return (text: string, offset: number): RegExpExecArray | null => {
+		const re = new RegExp(regex, 'y');
+		re.lastIndex = offset;
+		return re.exec(text);
+	};
+};
 
 /**
  * Statements ignored by Zenroom.
diff --git a/pkg/shared/tokens.test.ts b/pkg/shared/tokens.test.ts
index 17d50f74..2e4f9142 100644
--- a/pkg/shared/tokens.test.ts
+++ b/pkg/shared/tokens.test.ts
@@ -24,7 +24,7 @@ test('that identifiers are identified correctly', () => {
  'four' # blanks here and there	
      'five'  #	mix of blanks and tabs 	
 `;
-	// When I lex the it
+	// When I lex it
 	const lexed = lex(contract);
 	// Then I must have no errors
 	expect(lexed.errors).toHaveLength(0);
@@ -58,7 +58,7 @@ test('that identifiers are identified correctly', () => {
 	/* eslint-enable */
 });
 
-test('that non-matcheds error out', () => {
+test('non-matcheds error out', () => {
 	// Given I have a broken contract
 	const contract = `broken contract`;
 	// When I lex it
@@ -82,7 +82,7 @@ test('that non-matcheds error out', () => {
 	]);
 });
 
-test('that tokens are skipped correctly', () => {
+test('tokens are skipped correctly', () => {
 	// Given I have a contract with several ignored and an identifier tokens
 	const contract = "given I am 'alice'";
 	// When I lex it
diff --git a/pkg/shared/zenroom.test.ts b/pkg/shared/zenroom.test.ts
index e2474913..f5a11cca 100644
--- a/pkg/shared/zenroom.test.ts
+++ b/pkg/shared/zenroom.test.ts
@@ -1,6 +1,6 @@
-import { convZenParams } from './zenroom';
+import { convZenParams, zencodeExec, ZenroomError } from './zenroom';
 
-test('that convZenParams() works', () => {
+test('convZenParams() works', () => {
 	// Since TS already covers our butts regarding type checks, we just
 	// need to convice the coverage here that all the code paths are
 	// taken.
@@ -44,3 +44,25 @@ test('that convZenParams() works', () => {
 		expect(result).toStrictEqual({ data: JSON.stringify(data), keys: JSON.stringify(keys) });
 	}
 });
+
+describe('zencode()', () => {
+	test("doesn't throw with valid input", async () => {
+		// Given I have a valid contract
+		const contract = `Given I have nothing
+Then I print string 'I love you'
+`;
+		// When I execute the contract
+		const promise = zencodeExec(contract);
+		// Then it must not throw any errors
+		await expect(promise).resolves.toBeTruthy();
+	});
+
+	test('throws with invalid input', async () => {
+		// Given I have an invalid contract
+		const contract = "I'm invalid.";
+		// When I execute the contract
+		const promise = zencodeExec(contract);
+		// Then it must throw some errors
+		await expect(promise).rejects.toThrow(ZenroomError);
+	});
+});
diff --git a/pkg/shared/zenroom.ts b/pkg/shared/zenroom.ts
index a6d04ef8..18e70283 100644
--- a/pkg/shared/zenroom.ts
+++ b/pkg/shared/zenroom.ts
@@ -10,6 +10,16 @@ export type ZenroomResult = {
 	logs: string;
 };
 
+/**
+ * Error thrown by [zenroomExec] if contract execution somehow fails.
+ */
+export class ZenroomError extends Error {
+	constructor(logs: string) {
+		super(logs);
+		this.name = 'ZenroomError';
+	}
+}
+
 /**
  * Zenroom parameters suitable for zencode_exec() (after each value's
  * been piped to JSON.stringify()).
@@ -51,8 +61,15 @@ export const convZenParams = (params?: ZenroomParams): ZenroomStringParams => {
  * @param contract is a zencode contract.
  * @param params is parameters to Zenroom.
  * @returns the output of Zenroom.
+ * @throws {ZenroomError} if execution of a contract fails.
  */
 export const zencodeExec = async (
 	contract: string,
 	params?: ZenroomParams
-): Promise<ZenroomResult> => await zencode_exec(contract, convZenParams(params));
+): Promise<ZenroomResult> => {
+	try {
+		return await zencode_exec(contract, convZenParams(params));
+	} catch (e) {
+		throw new ZenroomError(e.logs);
+	}
+};
diff --git a/pnpm-workspace.yaml b/pnpm-workspace.yaml
index ed584239..30db7524 100644
--- a/pnpm-workspace.yaml
+++ b/pnpm-workspace.yaml
@@ -1,2 +1,2 @@
 packages:
-  - 'pkg/*'
+  - pkg/*