diff --git a/lib/kangaru.rb b/lib/kangaru.rb
index 2ee951f..701d4c7 100644
--- a/lib/kangaru.rb
+++ b/lib/kangaru.rb
@@ -9,9 +9,30 @@
 require "yaml"
 
 module Kangaru
-  Zeitwerk::Loader.for_gem(warn_on_extra_files: false).setup
+  INFLECTIONS = {
+    "rspec" => "RSpec"
+  }.freeze
+
+  @loader = Zeitwerk::Loader.for_gem(
+    warn_on_extra_files: false
+  ).tap do |loader|
+    loader.inflector.inflect(INFLECTIONS)
+    loader.setup
+  end
 
   class << self
     attr_accessor :application
+
+    def env=(value)
+      @env = value.to_sym
+    end
+
+    def env
+      @env ||= :runtime
+    end
+
+    def eager_load(namespace)
+      @loader.eager_load_namespace(namespace)
+    end
   end
 end
diff --git a/lib/kangaru/initialiser.rb b/lib/kangaru/initialiser.rb
index a1e7072..55aae43 100644
--- a/lib/kangaru/initialiser.rb
+++ b/lib/kangaru/initialiser.rb
@@ -22,6 +22,7 @@ def self.extended(namespace)
       source = caller[0].gsub(/:.*$/, "")
 
       Kangaru.application = Application.new(source:, namespace:)
+      Kangaru.eager_load(Initialisers)
 
       namespace.extend InjectedMethods
     end
diff --git a/lib/kangaru/initialisers/rspec.rb b/lib/kangaru/initialisers/rspec.rb
new file mode 100644
index 0000000..68c9341
--- /dev/null
+++ b/lib/kangaru/initialisers/rspec.rb
@@ -0,0 +1,11 @@
+module Kangaru
+  module Initialisers
+    module RSpec
+      if Object.const_defined?(:RSpec)
+        ::RSpec.configure do
+          Kangaru.env = :test
+        end
+      end
+    end
+  end
+end
diff --git a/sig/kangaru.rbs b/sig/kangaru.rbs
index 4135d43..c9fab43 100644
--- a/sig/kangaru.rbs
+++ b/sig/kangaru.rbs
@@ -1,10 +1,16 @@
 module Kangaru
   VERSION: String
+  INFLECTIONS: Hash[String, String]
 
   extend ClassMethods
 
   module ClassMethods
+    @loader: Zeitwerk::Loader
+
     attr_accessor application: Application
+    attr_accessor env: Symbol
+
+    def eager_load: (Module) -> void
   end
 
   # Included in target applications that extend Kangaru::Initialiser.
diff --git a/sig/kangaru/initialisers/rspec.rbs b/sig/kangaru/initialisers/rspec.rbs
new file mode 100644
index 0000000..36aca68
--- /dev/null
+++ b/sig/kangaru/initialisers/rspec.rbs
@@ -0,0 +1,6 @@
+module Kangaru
+  module Initialisers
+    module RSpec
+    end
+  end
+end
diff --git a/sig/zeitwerk/loader.rbs b/sig/zeitwerk/loader.rbs
new file mode 100644
index 0000000..b2ec374
--- /dev/null
+++ b/sig/zeitwerk/loader.rbs
@@ -0,0 +1,5 @@
+module Zeitwerk
+  class Loader
+    def eager_load_namespace: (Module) -> void
+  end
+end
diff --git a/spec/features/initialiser_spec.rb b/spec/features/initialiser_spec.rb
index 05c441d..2cc270e 100644
--- a/spec/features/initialiser_spec.rb
+++ b/spec/features/initialiser_spec.rb
@@ -10,88 +10,112 @@ class Foobar
     RUBY
   end
 
-  context "when the target gem does not extend the initialiser" do
-    before do
-      gem.main_file.write(<<~RUBY)
-        require "kangaru"
+  describe "initialising application" do
+    context "when the target gem does not extend the initialiser" do
+      before do
+        gem.main_file.write(<<~RUBY)
+          require "kangaru"
+
+          module SomeGem
+          end
+        RUBY
+      end
 
-        module SomeGem
-        end
-      RUBY
-    end
+      it "loads the gem module" do
+        expect { require_gem }
+          .to change { Object.const_defined?(:SomeGem) }
+          .from(false)
+          .to(true)
+      end
 
-    it "loads the gem module" do
-      expect { require_gem }
-        .to change { Object.const_defined?(:SomeGem) }
-        .from(false)
-        .to(true)
-    end
+      it "does not autoload gem files" do
+        expect { require_gem }
+          .not_to change { Object.const_defined?("SomeGem::Foobar") }
+          .from(false)
+      end
 
-    it "does not autoload gem files" do
-      expect { require_gem }
-        .not_to change { Object.const_defined?("SomeGem::Foobar") }
-        .from(false)
-    end
+      it "does not set the Kangaru application reference" do
+        expect { require_gem }.not_to change { Kangaru.application }.from(nil)
+      end
 
-    it "does not set the Kangaru application reference" do
-      expect { require_gem }.not_to change { Kangaru.application }.from(nil)
+      it "does not define the run! method in the gem's root module" do
+        require_gem
+        expect(SomeGem).not_to respond_to(:run!)
+      end
     end
 
-    it "does not define the run! method in the gem's root module" do
-      require_gem
-      expect(SomeGem).not_to respond_to(:run!)
-    end
-  end
+    context "when the target gem extends the initialiser" do
+      before do
+        gem.main_file.write(<<~RUBY)
+          require "kangaru"
 
-  context "when the target gem extends the initialiser" do
-    before do
-      gem.main_file.write(<<~RUBY)
-        require "kangaru"
+          module SomeGem
+            extend Kangaru::Initialiser
+          end
+        RUBY
+      end
 
-        module SomeGem
-          extend Kangaru::Initialiser
-        end
-      RUBY
-    end
+      it "loads the gem module" do
+        expect { require_gem }
+          .to change { Object.const_defined?("SomeGem") }
+          .from(false)
+          .to(true)
+      end
 
-    it "loads the gem module" do
-      expect { require_gem }
-        .to change { Object.const_defined?("SomeGem") }
-        .from(false)
-        .to(true)
-    end
+      it "autoloads gem files" do
+        expect { require_gem }
+          .to change { Object.const_defined?("SomeGem::Foobar") }
+          .from(false)
+          .to(true)
+      end
 
-    it "autoloads gem files" do
-      expect { require_gem }
-        .to change { Object.const_defined?("SomeGem::Foobar") }
-        .from(false)
-        .to(true)
-    end
+      it "sets the Kangaru application reference" do
+        expect { require_gem }
+          .to change { Kangaru.application }
+          .from(nil)
+          .to(a_kind_of(Kangaru::Application))
+      end
 
-    it "sets the Kangaru application reference" do
-      expect { require_gem }
-        .to change { Kangaru.application }
-        .from(nil)
-        .to(a_kind_of(Kangaru::Application))
-    end
+      it "defines the run! method in the gem's root module" do
+        require_gem
+        expect(SomeGem).to respond_to(:run!)
+      end
 
-    it "defines the run! method in the gem's root module" do
-      require_gem
-      expect(SomeGem).to respond_to(:run!)
-    end
+      describe "application reference" do
+        subject(:application) { Kangaru.application }
 
-    describe "application reference" do
-      subject(:application) { Kangaru.application }
+        before { require_gem }
 
-      before { require_gem }
+        it "sets the application source to the gem main file" do
+          expect(application.paths.source).to eq(gem.main_file)
+        end
 
-      it "sets the application source to the gem main file" do
-        expect(application.paths.source).to eq(gem.main_file)
+        it "sets the application name to the expected value" do
+          expect(application.paths.name).to eq("some_gem")
+        end
       end
+    end
+  end
 
-      it "sets the application name to the expected value" do
-        expect(application.paths.name).to eq("some_gem")
-      end
+  describe "setting test environment in RSpec" do
+    subject(:run_test) { gem.exec("rspec #{test_file}") }
+
+    let(:test_file) { gem.spec_path("test_spec") }
+
+    before do
+      test_file.write(<<~RUBY)
+        RSpec.describe do
+          it "sets the test environment" do
+            expect(Kangaru).to be_test
+          end
+        end
+      RUBY
+    end
+
+    include_context :kangaru_initialised
+
+    it "configures Kangaru to the test environment" do
+      expect(run_test).not_to include("FAILED")
     end
   end
 end
diff --git a/spec/kangaru/initialiser_spec.rb b/spec/kangaru/initialiser_spec.rb
index db589a5..a7e0dd1 100644
--- a/spec/kangaru/initialiser_spec.rb
+++ b/spec/kangaru/initialiser_spec.rb
@@ -5,6 +5,7 @@
     stub_const "Namespace", Module.new
 
     allow(Kangaru::Application).to receive(:new).and_return(application)
+    allow(Kangaru).to receive(:eager_load)
 
     allow_any_instance_of(Kernel).to receive(:caller).and_return([callsite])
   end
@@ -40,6 +41,15 @@
           .to change { Kangaru.application }
           .to(application)
       end
+
+      it "eager loads the Initialisers namespace" do
+        extended
+
+        expect(Kangaru)
+          .to have_received(:eager_load)
+          .with(Kangaru::Initialisers)
+          .once
+      end
     end
 
     context "when calling file is not in a gem structure" do
diff --git a/spec/kangaru_spec.rb b/spec/kangaru_spec.rb
new file mode 100644
index 0000000..fa00136
--- /dev/null
+++ b/spec/kangaru_spec.rb
@@ -0,0 +1,92 @@
+RSpec.describe Kangaru do
+  describe "@loader" do
+    subject(:loader) { described_class.instance_variable_get(:@loader) }
+
+    let(:lib_directory) { File.join(File.dirname(__dir__), "lib") }
+
+    it "sets the @loader instance variable" do
+      expect(described_class).to be_instance_variable_defined(:@loader)
+    end
+
+    it "sets the instance variable to a Zeitwerk loader" do
+      expect(loader).to be_a(Zeitwerk::Loader)
+    end
+
+    it "autoloads the lib directory" do
+      expect(loader.dirs).to include(lib_directory)
+    end
+  end
+
+  describe ".env=" do
+    subject(:set_env) { described_class.env = env }
+
+    def env_ivar = described_class.instance_variable_get(:@env)
+
+    after do
+      described_class.remove_instance_variable(:@env) if env_ivar
+    end
+
+    context "when env is a symbol" do
+      let(:env) { :env }
+
+      it "sets to a symbol" do
+        expect { set_env }.to change { env_ivar }.to(env)
+      end
+    end
+
+    context "when env is a string" do
+      let(:env) { "env" }
+
+      it "sets to a symbol" do
+        expect { set_env }.to change { env_ivar }.to(env.to_sym)
+      end
+    end
+  end
+
+  describe ".env" do
+    subject(:env) { described_class.env }
+
+    def env_ivar = described_class.instance_variable_get(:@env)
+
+    around do |spec|
+      described_class.remove_instance_variable(:@env) if env_ivar
+      spec.run
+      described_class.remove_instance_variable(:@env) if env_ivar
+    end
+
+    context "when env is not set" do
+      it "returns :runtime" do
+        expect(described_class.env).to eq(:runtime)
+      end
+    end
+
+    context "when env is set" do
+      before { described_class.env = env }
+
+      let(:env) { :foobar }
+
+      it "returns the set value" do
+        expect(described_class.env).to eq(env)
+      end
+    end
+  end
+
+  describe ".eager_load" do
+    subject(:eager_load) { described_class.eager_load(namespace) }
+
+    let(:namespace) { Module.new }
+
+    let(:loader) { described_class.instance_variable_get(:@loader) }
+
+    before { allow(loader).to receive(:eager_load_namespace) }
+
+    it "delegates to the zeitwerk loader" do
+      eager_load
+
+      expect(loader)
+        .to have_received(:eager_load_namespace)
+        .with(namespace)
+        .once
+    end
+  end
+end