diff --git a/Gemfile.lock b/Gemfile.lock
new file mode 100644
index 0000000..e094c87
--- /dev/null
+++ b/Gemfile.lock
@@ -0,0 +1,60 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    addressable (2.5.2)
+      public_suffix (>= 2.0.2, < 4.0)
+    claide (1.0.2)
+    claide-plugins (0.9.2)
+      cork
+      nap
+      open4 (~> 1.3)
+    colored2 (3.1.2)
+    cork (0.3.0)
+      colored2 (~> 3.1)
+    danger (5.5.11)
+      claide (~> 1.0)
+      claide-plugins (>= 0.9.2)
+      colored2 (~> 3.1)
+      cork (~> 0.1)
+      faraday (~> 0.9)
+      faraday-http-cache (~> 1.0)
+      git (~> 1)
+      kramdown (~> 1.5)
+      no_proxy_fix
+      octokit (~> 4.7)
+      terminal-table (~> 1)
+    danger-swiftlint (0.16.0)
+      danger
+      rake (> 10)
+      thor (~> 0.19)
+    faraday (0.14.0)
+      multipart-post (>= 1.2, < 3)
+    faraday-http-cache (1.3.1)
+      faraday (~> 0.8)
+    git (1.3.0)
+    kramdown (1.16.2)
+    multipart-post (2.0.0)
+    nap (1.1.0)
+    no_proxy_fix (0.1.2)
+    octokit (4.8.0)
+      sawyer (~> 0.8.0, >= 0.5.3)
+    open4 (1.3.4)
+    public_suffix (3.0.2)
+    rake (12.3.1)
+    sawyer (0.8.1)
+      addressable (>= 2.3.5, < 2.6)
+      faraday (~> 0.8, < 1.0)
+    terminal-table (1.8.0)
+      unicode-display_width (~> 1.1, >= 1.1.1)
+    thor (0.20.0)
+    unicode-display_width (1.3.0)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  danger
+  danger-swiftlint
+
+BUNDLED WITH
+   1.16.0
diff --git a/Tests/AddressTests.swift b/Tests/AddressTests.swift
index 54fdc32..998bf05 100644
--- a/Tests/AddressTests.swift
+++ b/Tests/AddressTests.swift
@@ -8,6 +8,11 @@ import TrustCore
 import XCTest
 
 class AddressTests: XCTestCase {
+    func testInvalid() {
+        XCTAssertNil(Address(string: "abc"))
+        XCTAssertNil(Address(eip55: "5aaeb6053f3e94c9b9a09f33669435e7ef1beaed"))
+    }
+
     func testEIP55() {
         XCTAssertEqual(
             Address(string: "5aaeb6053f3e94c9b9a09f33669435e7ef1beaed")!.eip55String,
@@ -30,4 +35,9 @@ class AddressTests: XCTestCase {
             "0xD1220A0cf47c7B9Be7A2E6BA89F429762e7b9aDb"
         )
     }
+
+    func testDescription() {
+        let address = Address(string: "5aaeb6053f3e94c9b9a09f33669435e7ef1beaed")!
+        XCTAssertEqual(address.description, "0x5aAeb6053F3E94C9b9A09f33669435E7Ef1BeAed")
+    }
 }
diff --git a/Tests/RLPTests.swift b/Tests/RLPTests.swift
index 0f3a276..ef437c0 100644
--- a/Tests/RLPTests.swift
+++ b/Tests/RLPTests.swift
@@ -60,4 +60,9 @@ class RLPTests: XCTestCase {
         print(encoded.hexString)
         XCTAssert(encoded.hexString.hasPrefix("f90400"))
     }
+
+    func testInvalid() {
+        XCTAssertNil(RLP.encode(-1))
+        XCTAssertNil(RLP.encode([0, -1]))
+    }
 }
diff --git a/TrustCore.xcodeproj/project.pbxproj b/TrustCore.xcodeproj/project.pbxproj
index 5499545..26ca9cc 100644
--- a/TrustCore.xcodeproj/project.pbxproj
+++ b/TrustCore.xcodeproj/project.pbxproj
@@ -221,7 +221,7 @@
 			isa = PBXProject;
 			attributes = {
 				LastSwiftUpdateCheck = 0920;
-				LastUpgradeCheck = 0920;
+				LastUpgradeCheck = 0930;
 				ORGANIZATIONNAME = Trust;
 				TargetAttributes = {
 					6149A69F201E433A00A2F35C = {
@@ -425,6 +425,7 @@
 				CLANG_WARN_BOOL_CONVERSION = YES;
 				CLANG_WARN_COMMA = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
 				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
 				CLANG_WARN_DOCUMENTATION_COMMENTS = YES;
 				CLANG_WARN_EMPTY_BODY = YES;
@@ -432,6 +433,7 @@
 				CLANG_WARN_INFINITE_RECURSION = YES;
 				CLANG_WARN_INT_CONVERSION = YES;
 				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
 				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
 				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
 				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
@@ -487,6 +489,7 @@
 				CLANG_WARN_BOOL_CONVERSION = YES;
 				CLANG_WARN_COMMA = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
 				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
 				CLANG_WARN_DOCUMENTATION_COMMENTS = YES;
 				CLANG_WARN_EMPTY_BODY = YES;
@@ -494,6 +497,7 @@
 				CLANG_WARN_INFINITE_RECURSION = YES;
 				CLANG_WARN_INT_CONVERSION = YES;
 				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
 				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
 				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
 				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
diff --git a/TrustCore.xcodeproj/xcshareddata/xcschemes/TrustCore.xcscheme b/TrustCore.xcodeproj/xcshareddata/xcschemes/TrustCore.xcscheme
index d513595..5216982 100644
--- a/TrustCore.xcodeproj/xcshareddata/xcschemes/TrustCore.xcscheme
+++ b/TrustCore.xcodeproj/xcshareddata/xcschemes/TrustCore.xcscheme
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0920"
+   LastUpgradeVersion = "0930"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
@@ -26,9 +26,8 @@
       buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
-      language = ""
-      shouldUseLaunchSchemeArgsEnv = "YES"
-      codeCoverageEnabled = "YES">
+      codeCoverageEnabled = "YES"
+      shouldUseLaunchSchemeArgsEnv = "YES">
       <Testables>
          <TestableReference
             skipped = "NO">
@@ -57,7 +56,6 @@
       buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
-      language = ""
       launchStyle = "0"
       useCustomWorkingDirectory = "NO"
       ignoresPersistentStateOnLaunch = "NO"
diff --git a/TrustCore.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist b/TrustCore.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist
new file mode 100644
index 0000000..18d9810
--- /dev/null
+++ b/TrustCore.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>