diff --git a/src/generator.ts b/src/generator.ts
index e05149c..d388eb7 100644
--- a/src/generator.ts
+++ b/src/generator.ts
@@ -1,5 +1,6 @@
 import { compile, compileFromFile, Options } from 'json-schema-to-typescript'
 import { flow } from 'lodash'
+import { JsonObject } from 'type-fest'
 
 /**
  * Options of json-schema-to-typescript.
@@ -48,9 +49,9 @@ function postProcess(source: string) {
  * Generate types from a JSON schema object.
  */
 export async function generateTypes(
-  schema: any,
+  schema: JsonObject,
   options: Partial<Options> = {}
-) {
+): Promise<string> {
   const mergedOptions = { ...defaultOptions, ...options }
   return await compile(schema, '', mergedOptions).then(postProcess)
 }
@@ -61,7 +62,7 @@ export async function generateTypes(
 export async function generateTypesFromFile(
   schemaPath: string,
   options: Partial<Options> = {}
-) {
+): Promise<string> {
   const mergedOptions = { ...defaultOptions, ...options }
   return await compileFromFile(schemaPath, mergedOptions).then(postProcess)
 }
diff --git a/src/loaders/loadArgs.test.ts b/src/loaders/loadArgs.test.ts
index 648c928..93090c1 100644
--- a/src/loaders/loadArgs.test.ts
+++ b/src/loaders/loadArgs.test.ts
@@ -1,6 +1,7 @@
+import { JsonObject } from 'type-fest'
 import { loadFromArgs } from './loadArgs'
 
-const TEST_CASES: [string, string[], {}][] = [
+const TEST_CASES: [string, string[], JsonObject][] = [
   ['camelCase a flag', ['--foo-bar'], { fooBar: true }],
   ['accept a value as option', ['--foo=bar'], { foo: 'bar' }],
   ['accept a value as flags', ['--foo', 'bar'], { foo: 'bar' }],
diff --git a/src/loaders/loadArgs.ts b/src/loaders/loadArgs.ts
index b13a269..36c8bf7 100644
--- a/src/loaders/loadArgs.ts
+++ b/src/loaders/loadArgs.ts
@@ -1,6 +1,7 @@
-import { camelCase, chain } from 'lodash'
 import getopts from 'getopts'
+import { camelCase, chain } from 'lodash'
 import { parseArray } from './utils'
+import { JsonObject } from 'type-fest'
 
 /**
  * Loads configuration from command line arguments.
@@ -8,14 +9,15 @@ import { parseArray } from './utils'
  * Arguments name describe a path to the desired options using `-` as
  * separator.
  *
- * @see https://github.com/jorgebucaran/getopts
  * @example
- *
- * --server-port=1337
- * --directives="['@graph0/directives', './directives']"
- * --directives=@graph0/directives --directives=./directives
+ * ```
+ * $ --cooking-time=200
+ * $ --types="['Fettuccine', 'Tagliatelle']"
+ * $ --directives=Fettuccine --directives=Tagliatelle
+ * ```
+ * @see https://github.com/jorgebucaran/getopts
  */
-export function loadFromArgs(args: string[]): {} {
+export function loadFromArgs(args: string[]): JsonObject {
   return chain(getopts(args))
     .omit('_')
     .mapKeys((_v, k) => camelCase(k))
diff --git a/src/loaders/loadEnv.test.ts b/src/loaders/loadEnv.test.ts
index eb6f927..980506c 100644
--- a/src/loaders/loadEnv.test.ts
+++ b/src/loaders/loadEnv.test.ts
@@ -1,20 +1,21 @@
+import { JsonObject } from 'type-fest'
 import { loadFromEnv } from './loadEnv'
 
-const TEST_CASES: [string, NodeJS.ProcessEnv, {}][] = [
+const TEST_CASES: [string, NodeJS.ProcessEnv, JsonObject][] = [
   [
     'map name to camelcase without namespace',
-    { FAUDA_FOO: 'bar' },
+    { PASTA_FOO: 'bar' },
     { foo: 'bar' }
   ],
   [
     'parse an array value',
-    { FAUDA_FOO: '["bar", 1337]' },
+    { PASTA_FOO: '["bar", 1337]' },
     { foo: ['bar', 1337] }
   ],
-  ['trim the value', { FAUDA_FOO: '  1337  ' }, { foo: '1337' }],
+  ['trim the value', { PASTA_FOO: '  1337  ' }, { foo: '1337' }],
   ['remove variables without namespace', { FOO: '1337' }, {}]
 ]
 
 test.each(TEST_CASES)('%s', (_title, env, expected) => {
-  expect(loadFromEnv(env, 'fauda')).toEqual(expected)
+  expect(loadFromEnv('pasta', env)).toEqual(expected)
 })
diff --git a/src/loaders/loadEnv.ts b/src/loaders/loadEnv.ts
index eca0667..f73c5bd 100644
--- a/src/loaders/loadEnv.ts
+++ b/src/loaders/loadEnv.ts
@@ -10,8 +10,8 @@ import { parseArray } from './utils'
  *
  * @example
  *
- * GRAPH0_SERVER_PORT=1337
- * GRAPH0_DIRECTIVES="['@graph0/directives', './directives']"
+ * PASTA_COOKING_TIME=200
+ * PASTA_TYPES="['Fettuccine', 'Tagliatelle']"
  */
 export function loadFromEnv(
   namespace: string,
diff --git a/src/loaders/loadFile.ts b/src/loaders/loadFile.ts
index d61ec83..41bf816 100644
--- a/src/loaders/loadFile.ts
+++ b/src/loaders/loadFile.ts
@@ -1,10 +1,11 @@
-import { cosmiconfig, Options as CosmiconfigOptions } from 'cosmiconfig'
 import loadTs from '@endemolshinegroup/cosmiconfig-typescript-loader'
+import { cosmiconfig, Options as CosmiconfigOptions } from 'cosmiconfig'
+import { JsonObject } from 'type-fest'
 
 /**
  * @internal
  */
-export function getDefaultSearchPlaces(namespace: string) {
+export function getDefaultSearchPlaces(namespace: string): string[] {
   return [
     'package.json',
     `.${namespace}rc`,
diff --git a/src/normalizer/expandVars.test.ts b/src/normalizer/expandVars.test.ts
index 805f754..fcba19f 100644
--- a/src/normalizer/expandVars.test.ts
+++ b/src/normalizer/expandVars.test.ts
@@ -1,6 +1,7 @@
+import { JsonObject } from 'type-fest'
 import { expandVars } from './expandVars'
 
-const TEST_CASES: [string, NodeJS.ProcessEnv, {}, {}][] = [
+const TEST_CASES: [string, NodeJS.ProcessEnv, JsonObject, JsonObject][] = [
   [
     'expand an existing env var to its value',
     { BAR: 'bar' },
diff --git a/src/normalizer/validate.test.ts b/src/normalizer/validate.test.ts
index 7c260d3..0ae4eb4 100644
--- a/src/normalizer/validate.test.ts
+++ b/src/normalizer/validate.test.ts
@@ -46,7 +46,8 @@ test('throw an error for invalid values', async () => {
   await expect(async () =>
     validate({ cookingTime: 'nope', seasoning: {} }, await getSchema())
   ).rejects.toThrowErrorMatchingInlineSnapshot(`
-    ".cookingTime should be number
-    .seasoning should be array"
-  `)
+          "validate: Validation failed
+          .cookingTime should be number
+          .seasoning should be array"
+        `)
 })
diff --git a/src/normalizer/validate.ts b/src/normalizer/validate.ts
index 47370e7..2b026d6 100644
--- a/src/normalizer/validate.ts
+++ b/src/normalizer/validate.ts
@@ -1,20 +1,21 @@
 import Ajv from 'ajv'
 import { chain } from 'lodash'
+import { JsonObject } from 'type-fest'
 
 function createError(errors: Ajv.ErrorObject[]): Error {
   const message = chain(errors)
     .map(err => `${err.dataPath} ${err.message}`)
     .join('\n')
     .value()
-  return new Error(message)
+  return new Error(`validate: Validation failed\n${message}`)
 }
 
 /**
  * @see https://github.com/ajv-validator/ajv
  */
 export function validate<Configuration>(
-  input: any,
-  schema: any
+  input: JsonObject,
+  schema: JsonObject
 ): Configuration {
   const ajv = new Ajv({
     allErrors: true,
@@ -28,8 +29,10 @@ export function validate<Configuration>(
   const isValid = ajv.validate(schema, output)
 
   if (!isValid) {
-    throw createError(ajv.errors!)
+    throw ajv.errors
+      ? createError(ajv.errors)
+      : new Error('validate: Unknown error')
   }
 
-  return output
+  return (output as unknown) as Configuration
 }
diff --git a/test/utils/testProject.ts b/test/utils/testProject.ts
index 0ff5a49..c788d49 100644
--- a/test/utils/testProject.ts
+++ b/test/utils/testProject.ts
@@ -11,7 +11,7 @@ export class TestProject {
     this.rootDir = path.join(FIXTURES_ROOT, snakeCase(variant))
   }
 
-  async setup() {
+  async setup(): Promise<void> {
     const { rootDir, variant } = this
     const variantDir = path.dirname(variant)
     const ext = path.extname(variant) || '.json'
@@ -29,7 +29,7 @@ export class TestProject {
     } catch (e) {}
   }
 
-  async teardown() {
+  async teardown(): Promise<void> {
     const { rootDir } = this
     await fs.rmdir(path.join(rootDir), { recursive: true })
   }