diff --git a/.rubocop.yml b/.rubocop.yml
index b7bd785..586f159 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,13 +1,15 @@
 require: rubocop-rspec
 
 RSpec/MultipleExpectations:
-  Max: 4
+  Max: 5
 RSpec/ContextWording:
   Enabled: false
-RSpec/FilePath:
-  SpecSuffixOnly: true
+RSpec/ExampleLength:
+  Max: 6
 RSpec/InstanceVariable:
   Enabled: false
+RSpec/SpecFilePathFormat:
+  Enabled: false
 
 AllCops:
   NewCops: enable
@@ -38,6 +40,8 @@ Style/RedundantBegin:
   Enabled: false   
 Style/SafeNavigation:
   Enabled: false
+Style/SlicingWithRange:
+  Enabled: false
 Layout/EmptyLineAfterGuardClause:
   Enabled: false
 Layout/CaseIndentation:
@@ -47,7 +51,7 @@ Layout/SpaceBeforeBlockBraces:
 Metrics/AbcSize:
   Enabled: false
 Metrics/BlockLength:
-  IgnoredMethods: ['describe', 'context']
+  AllowedMethods: ['describe', 'context']
 Metrics/ClassLength:
   Enabled: false
 Metrics/MethodLength:
@@ -56,6 +60,8 @@ Metrics/CyclomaticComplexity:
   Enabled: false
 Metrics/PerceivedComplexity:
   Enabled: false
+Naming/VariableNumber:
+  Enabled: false
 Naming/RescuedExceptionsVariableName:
   PreferredName: 'err'
 Naming/FileName:
diff --git a/lib/sys/darwin/sys/cpu.rb b/lib/sys/darwin/sys/cpu.rb
index e68b664..ca34dc6 100644
--- a/lib/sys/darwin/sys/cpu.rb
+++ b/lib/sys/darwin/sys/cpu.rb
@@ -43,7 +43,7 @@ class Error < StandardError; end
     CPU_ARCH_ABI64     = 0x01000000
     CPU_TYPE_X86       = 7
     CPU_TYPE_X86_64    = (CPU_TYPE_X86 | CPU_ARCH_ABI64)
-    CPU_TYPE_ARM		   = 12
+    CPU_TYPE_ARM       = 12
     CPU_TYPE_SPARC     = 14
     CPU_TYPE_POWERPC   = 18
     CPU_TYPE_POWERPC64 = CPU_TYPE_POWERPC | CPU_ARCH_ABI64
@@ -74,6 +74,7 @@ class Error < StandardError; end
     private_class_method :getloadavg
     private_class_method :sysconf
 
+    # Private wrapper class for struct clockinfo
     class ClockInfo < FFI::Struct
       layout(
         :hz, :int,
@@ -189,7 +190,7 @@ def self.freq
         (optr.read_long * clock[:hz]) / 1_000_000
       else
         if sysctlbyname('hw.cpufrequency', optr, size, nil, 0) < 0
-          raise Error, 'sysctlbyname failed on hw.cpufrequency' if result < 0
+          raise Error, 'sysctlbyname failed on hw.cpufrequency'
         end
         optr.read_long / 1_000_000
       end
diff --git a/lib/sys/linux/sys/cpu.rb b/lib/sys/linux/sys/cpu.rb
index 0052f9e..8472610 100644
--- a/lib/sys/linux/sys/cpu.rb
+++ b/lib/sys/linux/sys/cpu.rb
@@ -10,7 +10,10 @@ module Sys
 
   cpu_file  = '/proc/cpuinfo'
   cpu_hash  = {}
+
+  # rubocop:disable Style/MutableConstant
   CPU_ARRAY = []
+  # rubocop:enable Style/MutableConstant
 
   private_constant :CPU_ARRAY
 
diff --git a/lib/sys/unix/sys/cpu.rb b/lib/sys/unix/sys/cpu.rb
index 3e9f845..62d1ba9 100644
--- a/lib/sys/unix/sys/cpu.rb
+++ b/lib/sys/unix/sys/cpu.rb
@@ -92,6 +92,7 @@ class Error < StandardError; end
       # Do nothing, not supported on this platform.
     end
 
+    # Private wrapper class for the procinfo struct
     class ProcInfo < FFI::Struct
       layout(
         :pi_state, :int,
@@ -101,6 +102,8 @@ class ProcInfo < FFI::Struct
       )
     end
 
+    private_constant :ProcInfo
+
     # Returns the cpu's architecture. On most systems this will be identical
     # to the CPU.machine method. On OpenBSD it will be identical to the CPU.model
     # method.
diff --git a/spec/sys_cpu_bsd_spec.rb b/spec/sys_cpu_bsd_spec.rb
index 432fc09..de0738f 100644
--- a/spec/sys_cpu_bsd_spec.rb
+++ b/spec/sys_cpu_bsd_spec.rb
@@ -8,14 +8,14 @@
 require 'sys/cpu'
 require 'spec_helper'
 
-RSpec.describe Sys::CPU, :bsd => true do
+RSpec.describe Sys::CPU, :bsd do
   example 'architecture method basic functionality' do
     expect(described_class).to respond_to(:architecture)
     expect{ described_class.architecture }.not_to raise_error
   end
 
   example 'architecture method returns a sane value' do
-    expect(described_class.architecture).to be_kind_of(String)
+    expect(described_class.architecture).to be_a(String)
     expect(described_class.architecture.size).to be > 0
   end
 
@@ -29,7 +29,7 @@
   end
 
   example 'freq method returns expected value' do
-    expect(described_class.freq).to be_kind_of(Integer)
+    expect(described_class.freq).to be_a(Integer)
     expect(described_class.freq).to be > 0
   end
 
@@ -43,9 +43,9 @@
   end
 
   example 'load_avg returns the expected results' do
-    expect(described_class.load_avg).to be_kind_of(Array)
+    expect(described_class.load_avg).to be_a(Array)
     expect(described_class.load_avg.length).to eq(3)
-    expect(described_class.load_avg[0]).to be_kind_of(Float)
+    expect(described_class.load_avg[0]).to be_a(Float)
   end
 
   example 'load_avg does not accept any arguments' do
@@ -58,7 +58,7 @@
   end
 
   example 'machine method returns sane value' do
-    expect(described_class.machine).to be_kind_of(String)
+    expect(described_class.machine).to be_a(String)
     expect(described_class.machine.size).to be > 0
   end
 
@@ -72,7 +72,7 @@
   end
 
   example 'model method returns sane value' do
-    expect(described_class.model).to be_kind_of(String)
+    expect(described_class.model).to be_a(String)
     expect(described_class.model.length).to be > 0
   end
 
@@ -86,7 +86,7 @@
   end
 
   example 'num_cpu method returns expected value' do
-    expect(described_class.num_cpu).to be_kind_of(Integer)
+    expect(described_class.num_cpu).to be_a(Integer)
     expect(described_class.num_cpu).to be > 0
   end
 
@@ -94,8 +94,8 @@
     expect{ described_class.num_cpu(0) }.to raise_error(ArgumentError)
   end
 
-  context "ffi methods and constants are private" do
-    example "ffi constants are private" do
+  context 'ffi methods and constants are private' do
+    example 'ffi constants are private' do
       constants = described_class.constants
       expect(constants).not_to include(:CTL_HW)
       expect(constants).not_to include(:CPU_TYPE_X86)
@@ -104,13 +104,13 @@
       expect(constants).not_to include(:ClockInfo)
     end
 
-    example "ffi core methods are private" do
+    example 'ffi core methods are private' do
       methods = described_class.methods(false)
       expect(methods).not_to include(:attach_function)
       expect(methods).not_to include(:bitmask)
     end
 
-    example "ffi attached methods are private" do
+    example 'ffi attached methods are private' do
       methods = described_class.methods(false)
       expect(methods).not_to include(:sysctl)
       expect(methods).not_to include(:sysctlbyname)
diff --git a/spec/sys_cpu_hpux_spec.rb b/spec/sys_cpu_hpux_spec.rb
index 917c51b..3ef05a9 100644
--- a/spec/sys_cpu_hpux_spec.rb
+++ b/spec/sys_cpu_hpux_spec.rb
@@ -9,30 +9,30 @@
 require 'sys/cpu'
 require 'spec_helper'
 
-RSpec.describe Sys::CPU, :hpux => true do
+RSpec.describe Sys::CPU, :hpux do
   example 'cpu_freq' do
     expect(described_class).to respond_to(:freq)
     expect{ described_class.freq }.not_to raise_error
     expect{ described_class.freq(0) }.not_to raise_error
-    expect(described_class.freq).to be_kind_of(Integer)
+    expect(described_class.freq).to be_a(Integer)
   end
 
   example 'num_cpu' do
     expect(described_class).to respond_to(:num_cpu)
     expect{ described_class.num_cpu }.not_to raise_error
-    expect(described_class.num_cpu).to be_kind_of(Integer)
+    expect(described_class.num_cpu).to be_a(Integer)
   end
 
   example 'num_active_cpu' do
     expect(described_class).to respond_to(:num_active_cpu)
     expect{ described_class.num_active_cpu }.not_to raise_error
-    expect(described_class.num_active_cpu).to be_kind_of(Integer)
+    expect(described_class.num_active_cpu).to be_a(Integer)
   end
 
   example 'cpu_architecture' do
     expect(described_class).to respond_to(:architecture)
     expect{ described_class.architecture }.not_to raise_error
-    expect(described_class.architecture).to be_kind_of(String)
+    expect(described_class.architecture).to be_a(String)
   end
 
   example 'load_avg basic sanity check' do
@@ -47,8 +47,8 @@
   end
 
   example 'load_avg expected results' do
-    expect(described_class.load_avg).to be_kind_of(Array)
-    expect(described_class.load_avg(0)).to be_kind_of(Array)
+    expect(described_class.load_avg).to be_a(Array)
+    expect(described_class.load_avg(0)).to be_a(Array)
     expect(described_class.load_avg.length).to eq(3)
     expect(described_class.load_avg(0).length).to eq(3)
   end
diff --git a/spec/sys_cpu_linux_spec.rb b/spec/sys_cpu_linux_spec.rb
index f228cab..c30f986 100644
--- a/spec/sys_cpu_linux_spec.rb
+++ b/spec/sys_cpu_linux_spec.rb
@@ -9,7 +9,7 @@
 require 'sys/cpu'
 require 'spec_helper'
 
-RSpec.describe Sys::CPU, :linux => true do
+RSpec.describe Sys::CPU, :linux do
   example 'dynamic methods are defined as expected' do
     expect do
       described_class.processors do |cs|
@@ -25,28 +25,28 @@
 
   example 'cpu_stats works as expected' do
     expect{ described_class.cpu_stats }.not_to raise_error
-    expect(described_class.cpu_stats).to be_kind_of(Hash)
+    expect(described_class.cpu_stats).to be_a(Hash)
     expect(described_class.cpu_stats['cpu0'].length).to be >= 4
   end
 
   example 'architecture works as expected' do
     expect{ described_class.architecture }.not_to raise_error
-    expect(described_class.architecture).to be_kind_of(String)
+    expect(described_class.architecture).to be_a(String)
   end
 
   example 'model works as expected' do
     expect{ described_class.model }.not_to raise_error
-    expect(described_class.model).to be_kind_of(String)
+    expect(described_class.model).to be_a(String)
   end
 
   example 'freq works as expected' do
     expect{ described_class.freq }.not_to raise_error
-    expect(described_class.freq).to be_kind_of(Numeric)
+    expect(described_class.freq).to be_a(Numeric)
   end
 
   example 'num_cpu works as expected' do
     expect{ described_class.num_cpu }.not_to raise_error
-    expect(described_class.num_cpu).to be_kind_of(Numeric)
+    expect(described_class.num_cpu).to be_a(Numeric)
   end
 
   example 'bogus methods are not picked up by method_missing' do
diff --git a/spec/sys_cpu_windows_spec.rb b/spec/sys_cpu_windows_spec.rb
index 15a9160..109704d 100644
--- a/spec/sys_cpu_windows_spec.rb
+++ b/spec/sys_cpu_windows_spec.rb
@@ -10,20 +10,20 @@
 require 'sys/cpu'
 require 'socket'
 
-RSpec.describe Sys::CPU, :windows => true do
+RSpec.describe Sys::CPU, :windows do
   let(:host) { Socket.gethostname }
 
   example 'architecture' do
     expect(described_class).to respond_to(:architecture)
     expect{ described_class.architecture }.not_to raise_error
     expect{ described_class.architecture(host) }.not_to raise_error
-    expect(described_class.architecture).to be_kind_of(String)
+    expect(described_class.architecture).to be_a(String)
   end
 
   example 'freq basic functionality' do
     expect(described_class).to respond_to(:freq)
     expect{ described_class.freq }.not_to raise_error
-    expect(described_class.freq).to be_kind_of(Integer)
+    expect(described_class.freq).to be_a(Integer)
   end
 
   example 'freq with arguments' do
@@ -35,28 +35,28 @@
     expect(described_class).to respond_to(:model)
     expect{ described_class.model }.not_to raise_error
     expect{ described_class.model(host) }.not_to raise_error
-    expect(described_class.model).to be_kind_of(String)
+    expect(described_class.model).to be_a(String)
   end
 
   example 'num_cpu' do
     expect(described_class).to respond_to(:num_cpu)
     expect{ described_class.num_cpu }.not_to raise_error
     expect{ described_class.num_cpu(host) }.not_to raise_error
-    expect(described_class.num_cpu).to be_kind_of(Integer)
+    expect(described_class.num_cpu).to be_a(Integer)
   end
 
   example 'cpu_type' do
     expect(described_class).to respond_to(:cpu_type)
     expect{ described_class.cpu_type }.not_to raise_error
     expect{ described_class.cpu_type(host) }.not_to raise_error
-    expect(described_class.cpu_type).to be_kind_of(String)
+    expect(described_class.cpu_type).to be_a(String)
   end
 
   example 'load_avg' do
     expect(described_class).to respond_to(:load_avg)
     expect{ described_class.load_avg }.not_to raise_error
     expect{ described_class.load_avg(0, host) }.not_to raise_error
-    expect(described_class.load_avg).to be_kind_of(Integer).or be_kind_of(NilClass)
+    expect(described_class.load_avg).to be_a(Integer).or be_a(NilClass)
   end
 
   example 'processors' do