diff --git a/test/anyof.test.js b/test/anyof.test.js
index baa81060..b359761a 100644
--- a/test/anyof.test.js
+++ b/test/anyof.test.js
@@ -790,3 +790,23 @@ test('should build merged schemas twice', (t) => {
     t.assert.equal(stringify({ enums: 'BAR' }), '{"enums":"BAR"}')
   }
 })
+
+test('invalid anyOf schema', (t) => {
+  t.plan(1)
+
+  const schema = {
+    type: 'object',
+    properties: {
+      prop: {
+        anyOf: 'not array'  // invalid, anyOf must be array
+      }
+    }
+  }
+
+  try {
+    build(schema)
+    t.assert.fail('Should throw')
+  } catch (err) {
+    t.assert.ok(err.message.includes('schema is invalid'))
+  }
+})
diff --git a/test/array.test.js b/test/array.test.js
index dc643226..c00ef7e9 100644
--- a/test/array.test.js
+++ b/test/array.test.js
@@ -358,6 +358,28 @@ test('array items is a schema and additionalItems is false', (t) => {
   t.assert.equal(validate({ foo: ['foo', 'bar'] }), true)
 })
 
+test('array items is a list of schema and additionalItems is a schema', (t) => {
+  t.plan(1)
+
+  const schema = {
+    type: 'object',
+    properties: {
+      foo: {
+        type: 'array',
+        items: [
+          { type: 'string' }
+        ],
+        additionalItems: { type: 'number' }
+      }
+    }
+  }
+
+  const stringify = build(schema)
+  const result = stringify({ foo: ['foo', 42] })
+
+  t.assert.equal(result, '{"foo":["foo",42]}')
+})
+
 // https://github.com/fastify/fast-json-stringify/issues/279
 test('object array with anyOf and symbol', (t) => {
   t.plan(1)
diff --git a/test/debug-mode.test.js b/test/debug-mode.test.js
index 3e998a73..f6756bfe 100644
--- a/test/debug-mode.test.js
+++ b/test/debug-mode.test.js
@@ -119,3 +119,24 @@ test('debug should restore the same serializer instance', t => {
   const compiled = fjs.restore(debugMode)
   t.assert.equal(compiled(3.95), 4)
 })
+
+test('Serializer restoreFromState', t => {
+  t.plan(1)
+
+  const Serializer = require('../lib/serializer')
+  const serializer = new Serializer()
+  const state = serializer.getState()
+  const restored = Serializer.restoreFromState(state)
+  t.assert.ok(restored instanceof Serializer)
+})
+
+test('Validator restoreFromState', t => {
+  t.plan(1)
+
+  const Validator = require('../lib/validator')
+  const validator = new Validator()
+  validator.addSchema({ type: 'string' }, 'test')
+  const state = validator.getState()
+  const restored = Validator.restoreFromState(state)
+  t.assert.ok(restored instanceof Validator)
+})
diff --git a/test/if-then-else.test.js b/test/if-then-else.test.js
index dfe25e9b..804669e8 100644
--- a/test/if-then-else.test.js
+++ b/test/if-then-else.test.js
@@ -466,3 +466,75 @@ test('external recursive if/then/else', (t) => {
   const stringify = build(schema, { schema: { externalSchema } })
   t.assert.equal(stringify(data), '{"a":{"base":"a","bar":"42"},"b":{"base":"b","baz":"43"}}')
 })
+
+test('invalid if-then-else schema', (t) => {
+  t.plan(1)
+
+  const schema = {
+    type: 'object',
+    if: {
+      type: 'object',
+      properties: {
+        kind: { type: 'string', enum: ['foobar'] }
+      }
+    },
+    then: {
+      type: 'object',
+      properties: {
+        foo: { type: 'string' }
+      }
+    },
+    else: {
+      type: 'object',
+      properties: 'invalid'  // properties must be object
+    }
+  }
+
+  try {
+    build(schema)
+    t.assert.fail('Should throw')
+  } catch (err) {
+    t.assert.ok(err.message.includes('schema is invalid'))
+  }
+})
+
+test('if-then-else with allOf', (t) => {
+  t.plan(2)
+
+  const schema = {
+    type: 'object',
+    allOf: [
+      {
+        type: 'object',
+        properties: {
+          base: { type: 'string' }
+        }
+      }
+    ],
+    if: {
+      type: 'object',
+      properties: {
+        kind: { type: 'string', enum: ['foobar'] }
+      }
+    },
+    then: {
+      type: 'object',
+      properties: {
+        foo: { type: 'string' }
+      }
+    },
+    else: {
+      type: 'object',
+      properties: {
+        bar: { type: 'string' }
+      }
+    }
+  }
+
+  const stringify = build(schema)
+  const data = { base: 'test', kind: 'foobar', foo: 'value' }
+  const output = stringify(data)
+
+  t.assert.doesNotThrow(() => JSON.parse(output))
+  t.assert.equal(output, '{"base":"test","foo":"value"}')
+})
diff --git a/test/invalidSchema.test.js b/test/invalidSchema.test.js
index 4402484b..966b6d79 100644
--- a/test/invalidSchema.test.js
+++ b/test/invalidSchema.test.js
@@ -16,3 +16,23 @@ test('Should throw on invalid schema', t => {
     })
   }, { message: /^"invalid" schema is invalid:.*/ })
 })
+
+test('invalid not schema', (t) => {
+  t.plan(1)
+
+  const schema = {
+    type: 'object',
+    properties: {
+      prop: {
+        not: 'not object'  // invalid, not must be object
+      }
+    }
+  }
+
+  try {
+    build(schema)
+    t.assert.fail('Should throw')
+  } catch (err) {
+    t.assert.ok(err.message.includes('schema is invalid'))
+  }
+})
diff --git a/test/oneof.test.js b/test/oneof.test.js
index f3b29f4b..01c2f3bf 100644
--- a/test/oneof.test.js
+++ b/test/oneof.test.js
@@ -488,3 +488,23 @@ test('all array items does not match oneOf types', (t) => {
 
   t.assert.throws(() => stringify({ data: [null, false, true, undefined, [], {}] }))
 })
+
+test('invalid oneOf schema', (t) => {
+  t.plan(1)
+
+  const schema = {
+    type: 'object',
+    properties: {
+      prop: {
+        oneOf: 'not array'  // invalid, oneOf must be array
+      }
+    }
+  }
+
+  try {
+    build(schema)
+    t.assert.fail('Should throw')
+  } catch (err) {
+    t.assert.ok(err.message.includes('schema is invalid'))
+  }
+})
diff --git a/test/ref.test.js b/test/ref.test.js
index eae4703a..2f736445 100644
--- a/test/ref.test.js
+++ b/test/ref.test.js
@@ -2044,3 +2044,34 @@ test('ref internal - throw if schema has definition twice with different shape',
     t.assert.equal(err.message, 'There is already another anchor "#uri" in schema "test".')
   }
 })
+
+test('ref nested', (t) => {
+  t.plan(2)
+
+  const schema = {
+    definitions: {
+      def1: {
+        $ref: '#/definitions/def2'
+      },
+      def2: {
+        type: 'string'
+      }
+    },
+    type: 'object',
+    properties: {
+      str: {
+        $ref: '#/definitions/def1'
+      }
+    }
+  }
+
+  const object = {
+    str: 'test'
+  }
+
+  const stringify = build(schema)
+  const output = stringify(object)
+
+  t.assert.doesNotThrow(() => JSON.parse(output))
+  t.assert.equal(output, '{"str":"test"}')
+})