diff --git a/package.json b/package.json
index 1c20abb..8a4ca67 100644
--- a/package.json
+++ b/package.json
@@ -10,7 +10,7 @@
     "lint:fix": "eslint --fix",
     "test": "npm run test:unit && npm run test:typescript",
     "test:unit": "c8 --100 node --test",
-    "test:typescript": "tsd"
+    "test:typescript": "tstyche"
   },
   "repository": {
     "type": "git",
@@ -71,6 +71,6 @@
     "eslint": "^9.17.0",
     "fluent-json-schema": "^6.0.0",
     "neostandard": "^0.13.0",
-    "tsd": "^0.33.0"
+    "tstyche": "^7.0.0"
   }
-}
+}
\ No newline at end of file
diff --git a/types/index.test-d.ts b/types/index.tst.ts
similarity index 53%
rename from types/index.test-d.ts
rename to types/index.tst.ts
index dace7a6..2cc1ff7 100644
--- a/types/index.test-d.ts
+++ b/types/index.tst.ts
@@ -1,11 +1,11 @@
-import { expectError, expectType } from 'tsd'
+import { expect } from 'tstyche'
 import envSchema, {
   EnvSchemaData,
   EnvSchemaOpt,
   keywords,
   envSchema as envSchemaNamed,
   default as envSchemaDefault,
-} from '..'
+} from '.'
 import Ajv, { KeywordDefinition, JSONSchemaType } from 'ajv'
 import { Static, Type } from 'typebox'
 
@@ -34,62 +34,62 @@ const data = {
   foo: 'bar',
 }
 
-expectType<EnvSchemaData>(envSchema())
-expectType<EnvSchemaData>(envSchemaNamed())
-expectType<EnvSchemaData>(envSchemaDefault())
+expect(envSchema()).type.toBe<EnvSchemaData | unknown>()
+expect(envSchemaNamed()).type.toBe<EnvSchemaData | unknown>()
+expect(envSchemaDefault()).type.toBe<EnvSchemaData | unknown>()
 
 const emptyOpt: EnvSchemaOpt = {}
-expectType<EnvSchemaOpt>(emptyOpt)
+expect(emptyOpt).type.toBe<EnvSchemaOpt>()
 
 const optWithSchemaTypebox: EnvSchemaOpt = {
   schema: schemaTypebox,
 }
-expectType<EnvSchemaOpt>(optWithSchemaTypebox)
+expect(optWithSchemaTypebox).type.toBe<EnvSchemaOpt>()
 
 const optWithSchemaWithType: EnvSchemaOpt<EnvData> = {
   schema: schemaWithType,
 }
-expectType<EnvSchemaOpt<EnvData>>(optWithSchemaWithType)
+expect(optWithSchemaWithType).type.toBe<EnvSchemaOpt<EnvData>>()
 
 const optWithData: EnvSchemaOpt = {
   data,
 }
-expectType<EnvSchemaOpt>(optWithData)
+expect(optWithData).type.toBe<EnvSchemaOpt>()
 
-expectError<EnvSchemaOpt>({
-  data: [], // min 1 item
+expect<EnvSchemaOpt>().type.not.toBeAssignableFrom({
+  data: [],
 })
 
 const optWithArrayData: EnvSchemaOpt = {
   data: [{}],
 }
-expectType<EnvSchemaOpt>(optWithArrayData)
+expect(optWithArrayData).type.toBe<EnvSchemaOpt>()
 
 const optWithMultipleItemArrayData: EnvSchemaOpt = {
   data: [{}, {}],
 }
-expectType<EnvSchemaOpt>(optWithMultipleItemArrayData)
+expect(optWithMultipleItemArrayData).type.toBe<EnvSchemaOpt>()
 
 const optWithDotEnvBoolean: EnvSchemaOpt = {
   dotenv: true,
 }
-expectType<EnvSchemaOpt>(optWithDotEnvBoolean)
+expect(optWithDotEnvBoolean).type.toBe<EnvSchemaOpt>()
 
 const optWithDotEnvOpt: EnvSchemaOpt = {
   dotenv: {},
 }
-expectType<EnvSchemaOpt>(optWithDotEnvOpt)
+expect(optWithDotEnvOpt).type.toBe<EnvSchemaOpt>()
 
 const optWithEnvExpand: EnvSchemaOpt = {
   expandEnv: true,
 }
-expectType<EnvSchemaOpt>(optWithEnvExpand)
+expect(optWithEnvExpand).type.toBe<EnvSchemaOpt>()
 
 const optWithAjvInstance: EnvSchemaOpt = {
   ajv: new Ajv(),
 }
-expectType<EnvSchemaOpt>(optWithAjvInstance)
-expectType<KeywordDefinition>(envSchema.keywords.separator)
+expect(optWithAjvInstance).type.toBe<EnvSchemaOpt>()
+expect(envSchema.keywords.separator).type.toBe<KeywordDefinition>()
 
 const optWithAjvCustomOptions: EnvSchemaOpt = {
   ajv: {
@@ -98,18 +98,20 @@ const optWithAjvCustomOptions: EnvSchemaOpt = {
     },
   },
 }
-expectType<EnvSchemaOpt>(optWithAjvCustomOptions)
-expectError<EnvSchemaOpt>({
-  ajv: {
-    customOptions (_ajvInstance: Ajv) {},
-  },
-})
+expect(optWithAjvCustomOptions).type.toBe<EnvSchemaOpt>()
+
+expect<EnvSchemaOpt>()
+  .type.not.toBeAssignableFrom({
+    ajv: {
+      customOptions (_ajvInstance: Ajv) {}
+    }
+  })
 
 const envSchemaWithType = envSchema({ schema: schemaWithType })
-expectType<EnvData>(envSchemaWithType)
+expect(envSchemaWithType).type.toBe<EnvData>()
 
 const envSchemaTypebox = envSchema<SchemaTypebox>({ schema: schemaTypebox })
-expectType<SchemaTypebox>(envSchemaTypebox)
+expect(envSchemaTypebox).type.toBe<SchemaTypebox>()
 
-expectType<KeywordDefinition>(keywords.separator)
-expectType<KeywordDefinition>(envSchema.keywords.separator)
+expect(keywords.separator).type.toBe<KeywordDefinition>()
+expect(envSchema.keywords.separator).type.toBe<KeywordDefinition>()