diff --git a/src/spectator/expectation.cr b/src/spectator/expectation.cr
index 848630d..cfaa6ae 100644
--- a/src/spectator/expectation.cr
+++ b/src/spectator/expectation.cr
@@ -106,17 +106,6 @@ module Spectator
         report(match_data, message)
       end
 
-      def to(stub : Mocks::MethodStub) : Nil
-        Harness.current.mocks.expect(@expression.value, stub)
-        value = Value.new(stub.name, stub.to_s)
-        matcher = Matchers::ReceiveMatcher.new(value, stub.arguments?)
-        to_eventually(matcher)
-      end
-
-      def to(stubs : Enumerable(Mocks::MethodStub)) : Nil
-        stubs.each { |stub| to(stub) }
-      end
-
       # Asserts that some criteria defined by the matcher is not satisfied.
       # This is effectively the opposite of `#to`.
       # Allows a custom message to be used.
@@ -131,24 +120,6 @@ module Spectator
         to_not(matcher, message)
       end
 
-      def to_not(stub : Mocks::MethodStub) : Nil
-        value = Value.new(stub.name, stub.to_s)
-        matcher = Matchers::ReceiveMatcher.new(value, stub.arguments?)
-        to_never(matcher)
-      end
-
-      def not_to(stub : Mocks::MethodStub) : Nil
-        to_not(stub)
-      end
-
-      def to_not(stubs : Enumerable(Mocks::MethodStub)) : Nil
-        stubs.each { |stub| to_not(stub) }
-      end
-
-      def not_to(stubs : Enumerable(Mocks::MethodStub)) : Nil
-        to_not(stubs)
-      end
-
       # Asserts that some criteria defined by the matcher is eventually satisfied.
       # The expectation is checked after the example finishes and all hooks have run.
       # Allows a custom message to be used.
@@ -156,14 +127,6 @@ module Spectator
         Harness.current.defer { to(matcher, message) }
       end
 
-      def to_eventually(stub : Mocks::MethodStub) : Nil
-        to(stub)
-      end
-
-      def to_eventually(stubs : Enumerable(Mocks::MethodStub)) : Nil
-        to(stub)
-      end
-
       # Asserts that some criteria defined by the matcher is never satisfied.
       # The expectation is checked after the example finishes and all hooks have run.
       # Allows a custom message to be used.
@@ -177,14 +140,6 @@ module Spectator
         to_never(matcher, message)
       end
 
-      def to_never(stub : Mocks::MethodStub) : Nil
-        to_not(stub)
-      end
-
-      def to_never(stub : Enumerable(Mocks::MethodStub)) : Nil
-        to_not(stub)
-      end
-
       # Reports an expectation to the current harness.
       private def report(match_data : Matchers::MatchData, message : String? | Proc(String) = nil)
         expectation = Expectation.new(match_data, @location, message)
diff --git a/src/spectator/harness.cr b/src/spectator/harness.cr
index 37c27f3..ec21d51 100644
--- a/src/spectator/harness.cr
+++ b/src/spectator/harness.cr
@@ -3,7 +3,6 @@ require "./example_failed"
 require "./example_pending"
 require "./expectation"
 require "./expectation_failed"
-require "./mocks"
 require "./multiple_expectations_failed"
 require "./pass_result"
 require "./result"
@@ -39,8 +38,6 @@ module Spectator
     # Retrieves the harness for the current running example.
     class_getter! current : self
 
-    getter mocks = Mocks::Registry.new
-
     # Wraps an example with a harness and runs test code.
     # A block provided to this method is considered to be the test code.
     # The value of `.current` is set to the harness for the duration of the test.
@@ -134,7 +131,6 @@ module Spectator
       elapsed = Time.measure do
         error = catch { yield }
       end
-      error = nil if error.is_a?(SystemExit) && mocks.exit_handled?
       {elapsed, error}
     end
 
diff --git a/src/spectator/matchers/receive_matcher.cr b/src/spectator/matchers/receive_matcher.cr
deleted file mode 100644
index 7f3d233..0000000
--- a/src/spectator/matchers/receive_matcher.cr
+++ /dev/null
@@ -1,126 +0,0 @@
-require "../mocks"
-require "./standard_matcher"
-
-module Spectator::Matchers
-  struct ReceiveMatcher < StandardMatcher
-    alias Range = ::Range(Int32, Int32) | ::Range(Nil, Int32) | ::Range(Int32, Nil)
-
-    def initialize(@expected : Expression(Symbol), @args : Mocks::Arguments? = nil, @range : Range? = nil)
-    end
-
-    def description : String
-      range = @range
-      "received message #{@expected.label} #{range ? "#{humanize_range(range)} time(s)" : "At least once"} with #{@args || "any arguments"}"
-    end
-
-    def match?(actual : Expression(T)) : Bool forall T
-      calls = Harness.current.mocks.calls_for(actual.value, @expected.value)
-      calls.select! { |call| @args === call.args } if @args
-      if (range = @range)
-        range.includes?(calls.size)
-      else
-        !calls.empty?
-      end
-    end
-
-    def failure_message(actual : Expression(T)) : String forall T
-      range = @range
-      "#{actual.label} did not receive #{@expected.label} #{range ? "#{humanize_range(range)} time(s)" : "at least once"} with #{@args || "any arguments"}"
-    end
-
-    def failure_message_when_negated(actual) : String
-      range = @range
-      "#{actual.label} received #{@expected.label} #{range ? "#{humanize_range(range)} time(s)" : "at least once"} with #{@args || "any arguments"}"
-    end
-
-    def values(actual : Expression(T)) forall T
-      calls = Harness.current.mocks.calls_for(actual.value, @expected.value)
-      calls.select! { |call| @args === call.args } if @args
-      range = @range
-      {
-        expected: "#{range ? "#{humanize_range(range)} time(s)" : "At least once"} with #{@args || "any arguments"}",
-        received: "#{calls.size} time(s)",
-      }
-    end
-
-    def negated_values(actual : Expression(T)) forall T
-      calls = Harness.current.mocks.calls_for(actual.value, @expected.value)
-      calls.select! { |call| @args === call.args } if @args
-      range = @range
-      {
-        expected: "#{range ? "Not #{humanize_range(range)} time(s)" : "Never"} with #{@args || "any arguments"}",
-        received: "#{calls.size} time(s)",
-      }
-    end
-
-    def with(*args, **opts)
-      args = Mocks::GenericArguments.new(args, opts)
-      ReceiveMatcher.new(@expected, args, @range)
-    end
-
-    def once
-      ReceiveMatcher.new(@expected, @args, (1..1))
-    end
-
-    def twice
-      ReceiveMatcher.new(@expected, @args, (2..2))
-    end
-
-    def exactly(count)
-      Count.new(@expected, @args, (count..count))
-    end
-
-    def at_least(count)
-      Count.new(@expected, @args, (count..))
-    end
-
-    def at_most(count)
-      Count.new(@expected, @args, (..count))
-    end
-
-    def at_least_once
-      at_least(1).times
-    end
-
-    def at_least_twice
-      at_least(2).times
-    end
-
-    def at_most_once
-      at_most(1).times
-    end
-
-    def at_most_twice
-      at_most(2).times
-    end
-
-    def humanize_range(range : Range)
-      if (min = range.begin)
-        if (max = range.end)
-          if min == max
-            min
-          else
-            "#{min} to #{max}"
-          end
-        else
-          "At least #{min}"
-        end
-      else
-        if (max = range.end)
-          "At most #{max}"
-        else
-          raise "Unexpected endless range"
-        end
-      end
-    end
-
-    private struct Count
-      def initialize(@expected : Expression(Symbol), @args : Mocks::Arguments?, @range : Range)
-      end
-
-      def times
-        ReceiveMatcher.new(@expected, @args, @range)
-      end
-    end
-  end
-end
diff --git a/src/spectator/matchers/receive_type_matcher.cr b/src/spectator/matchers/receive_type_matcher.cr
deleted file mode 100644
index 362707d..0000000
--- a/src/spectator/matchers/receive_type_matcher.cr
+++ /dev/null
@@ -1,126 +0,0 @@
-require "../mocks"
-require "./standard_matcher"
-
-module Spectator::Matchers
-  struct ReceiveTypeMatcher < StandardMatcher
-    alias Range = ::Range(Int32, Int32) | ::Range(Nil, Int32) | ::Range(Int32, Nil)
-
-    def initialize(@expected : Expression(Symbol), @args : Mocks::Arguments? = nil, @range : Range? = nil)
-    end
-
-    def description : String
-      range = @range
-      "received message #{@expected.label} #{range ? "#{humanize_range(range)} time(s)" : "At least once"} with #{@args || "any arguments"}"
-    end
-
-    def match?(actual : Expression(T)) : Bool forall T
-      calls = Harness.current.mocks.calls_for_type(actual.value, @expected.value)
-      calls.select! { |call| @args === call.args } if @args
-      if (range = @range)
-        range.includes?(calls.size)
-      else
-        !calls.empty?
-      end
-    end
-
-    def failure_message(actual : Expression(T)) : String forall T
-      range = @range
-      "#{actual.label} did not receive #{@expected.label} #{range ? "#{humanize_range(range)} time(s)" : "at least once"} with #{@args || "any arguments"}"
-    end
-
-    def failure_message_when_negated(actual : Expression(T)) : String forall T
-      range = @range
-      "#{actual.label} received #{@expected.label} #{range ? "#{humanize_range(range)} time(s)" : "at least once"} with #{@args || "any arguments"}"
-    end
-
-    def values(actual : Expression(T)) forall T
-      calls = Harness.current.mocks.calls_for_type(T, @expected.value)
-      calls.select! { |call| @args === call.args } if @args
-      range = @range
-      {
-        expected: "#{range ? "#{humanize_range(range)} time(s)" : "At least once"} with #{@args || "any arguments"}",
-        received: "#{calls.size} time(s)",
-      }
-    end
-
-    def negated_values(actual : Expression(T)) forall T
-      calls = Harness.current.mocks.calls_for_type(T, @expected.value)
-      calls.select! { |call| @args === call.args } if @args
-      range = @range
-      {
-        expected: "#{range ? "Not #{humanize_range(range)} time(s)" : "Never"} with #{@args || "any arguments"}",
-        received: "#{calls.size} time(s)",
-      }
-    end
-
-    def with(*args, **opts)
-      args = Mocks::GenericArguments.new(args, opts)
-      ReceiveTypeMatcher.new(@expected, args, @range)
-    end
-
-    def once
-      ReceiveTypeMatcher.new(@expected, @args, (1..1))
-    end
-
-    def twice
-      ReceiveTypeMatcher.new(@expected, @args, (2..2))
-    end
-
-    def exactly(count)
-      Count.new(@expected, @args, (count..count))
-    end
-
-    def at_least(count)
-      Count.new(@expected, @args, (count..))
-    end
-
-    def at_most(count)
-      Count.new(@expected, @args, (..count))
-    end
-
-    def at_least_once
-      at_least(1).times
-    end
-
-    def at_least_twice
-      at_least(2).times
-    end
-
-    def at_most_once
-      at_most(1).times
-    end
-
-    def at_most_twice
-      at_most(2).times
-    end
-
-    def humanize_range(range : Range)
-      if (min = range.begin)
-        if (max = range.end)
-          if min == max
-            min
-          else
-            "#{min} to #{max}"
-          end
-        else
-          "At least #{min}"
-        end
-      else
-        if (max = range.end)
-          "At most #{max}"
-        else
-          raise "Unexpected endless range"
-        end
-      end
-    end
-
-    private struct Count
-      def initialize(@expected : Expression(Symbol), @args : Mocks::Arguments?, @range : Range)
-      end
-
-      def times
-        ReceiveTypeMatcher.new(@expected, @args, @range)
-      end
-    end
-  end
-end
diff --git a/src/spectator/mocks.cr b/src/spectator/mocks.cr
index b72ffea..f50bf9e 100644
--- a/src/spectator/mocks.cr
+++ b/src/spectator/mocks.cr
@@ -1,18 +1,7 @@
 require "./mocks/*"
-require "./system_exit"
 
 module Spectator
   # Functionality for mocking existing types.
   module Mocks
   end
 end
-
-# Add default stub to `exit` method.
-# This captures *most* (technically not all) attempts to exit the process.
-# This stub only takes effect in example code.
-# It intercepts `exit` calls and raises `Spectator::SystemExit` to prevent killing the test.
-# class ::Process
-#   include ::Spectator::Mocks::Stubs
-
-#   stub self.exit(code) { raise ::Spectator::SystemExit.new }
-# end
diff --git a/src/spectator/system_exit.cr b/src/spectator/system_exit.cr
deleted file mode 100644
index bdb0aea..0000000
--- a/src/spectator/system_exit.cr
+++ /dev/null
@@ -1,5 +0,0 @@
-module Spectator
-  # Exception raised when `exit` is called and intercepted from a stub.
-  class SystemExit < Exception
-  end
-end