diff --git a/HW03/Dmitry_Susha/.rspec b/HW03/Dmitry_Susha/.rspec
new file mode 100644
index 00000000..c99d2e73
--- /dev/null
+++ b/HW03/Dmitry_Susha/.rspec
@@ -0,0 +1 @@
+--require spec_helper
diff --git a/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_01.rb b/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_01.rb
index c614a151..0ef6fcd9 100644
--- a/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_01.rb
+++ b/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_01.rb
@@ -2,6 +2,8 @@
 
 class Homework3
   def task1(logs)
+    return '' unless logs.is_a?(String)
+
     logs.split("\n").select { |string| string.downcase.include?('error') }[0].to_s
   end
 end
diff --git a/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_02.rb b/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_02.rb
index 835ec157..2ac835e5 100644
--- a/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_02.rb
+++ b/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_02.rb
@@ -3,9 +3,10 @@
 class Homework3
   FORMAT_STRING = %r{^(?:[0-9]{1,3}\.){3}[0-9]{1,3} - - \[\d*/\w*/\d*:\d*:\d*:\d* \+\d*\] "\w* /\w*/\d/\w*}
   def task2(logs)
+    return [] unless logs.is_a?(String)
+
     lines = logs.split("\n")
-    lines.select { |string| check_format?(string) }
-         .map { |string| make_output(string) }
+    lines.select { |string| check_format?(string) }.map { |string| make_output(string) }
   end
 
   private
diff --git a/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_03.rb b/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_03.rb
index 1da73301..174cd421 100644
--- a/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_03.rb
+++ b/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_03.rb
@@ -4,6 +4,8 @@
 class Homework3
   START_EVENT_LINE = /Calling core with action:/
   def task3(logs)
+    return '0' unless logs.is_a?(String)
+
     lines = logs.split("\n")
     start_event_lines = lines.select { |string| string.match?(START_EVENT_LINE) }
     return '0' if start_event_lines.size < 2
diff --git a/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_04.rb b/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_04.rb
index da9c8b55..67690158 100644
--- a/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_04.rb
+++ b/HW03/Dmitry_Susha/dmitry_susha_hw_03_t_04.rb
@@ -2,6 +2,8 @@
 
 class Homework3
   def task4(string)
+    return { letters: 0, digits: 0 } unless string.is_a?(String)
+
     letters = string.count('a-zA-Z')
     digits = string.count('0-9')
     { letters: letters, digits: digits }
diff --git a/HW03/Dmitry_Susha/spec/dmitry_susha_hw_03_t_01_spec.rb b/HW03/Dmitry_Susha/spec/dmitry_susha_hw_03_t_01_spec.rb
new file mode 100644
index 00000000..76d70c1c
--- /dev/null
+++ b/HW03/Dmitry_Susha/spec/dmitry_susha_hw_03_t_01_spec.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+RSpec.describe Homework3 do
+  subject { described_class.new }
+
+  describe 'task 1' do
+    context 'when text wrong' do
+      it 'returns an empty string' do
+        expect(subject.task1('sadhfksjadfhksahdf')).to eq('')
+      end
+    end
+
+    context 'when log is array' do
+      it 'returns an empty string' do
+        expect(subject.task1([])).to eq('')
+      end
+    end
+
+    context 'when log is hash' do
+      it 'returns an empty string' do
+        expect(subject.task1({})).to eq('')
+      end
+    end
+
+    context 'when log is nil' do
+      it 'returns an empty string' do
+        expect(subject.task1(nil)).to eq('')
+      end
+    end
+
+    context 'when log is number' do
+      it 'returns an empty string' do
+        expect(subject.task1(1)).to eq('')
+      end
+    end
+  end
+end
diff --git a/HW03/Dmitry_Susha/spec/dmitry_susha_hw_03_t_02_spec.rb b/HW03/Dmitry_Susha/spec/dmitry_susha_hw_03_t_02_spec.rb
new file mode 100644
index 00000000..b6ef4563
--- /dev/null
+++ b/HW03/Dmitry_Susha/spec/dmitry_susha_hw_03_t_02_spec.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+RSpec.describe Homework3 do
+  subject { described_class.new }
+
+  describe 'task 2' do
+    context 'when text is wrong' do
+      it 'returns an  empty array' do
+        expect(subject.task2('sadhfksjadfhksahdf')).to eq([])
+      end
+    end
+
+    context 'when log is array' do
+      it 'returns an empty array' do
+        expect(subject.task2([])).to eq([])
+      end
+    end
+
+    context 'when log is hash' do
+      it 'returns an empty array' do
+        expect(subject.task2({})).to eq([])
+      end
+    end
+
+    context 'when log is nil' do
+      it 'returns an empty array' do
+        expect(subject.task2(nil)).to eq([])
+      end
+    end
+
+    context 'when log is number' do
+      it 'returns an empty array' do
+        expect(subject.task2(1)).to eq([])
+      end
+    end
+  end
+end
diff --git a/HW03/Dmitry_Susha/spec/dmitry_susha_hw_03_t_03_spec.rb b/HW03/Dmitry_Susha/spec/dmitry_susha_hw_03_t_03_spec.rb
new file mode 100644
index 00000000..d611522d
--- /dev/null
+++ b/HW03/Dmitry_Susha/spec/dmitry_susha_hw_03_t_03_spec.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+RSpec.describe Homework3 do
+  subject { described_class.new }
+
+  describe 'task 3' do
+    context 'when text wrong' do
+      it 'returns "0"' do
+        expect(subject.task3('sadhfksjadfhksahdf')).to eq('0')
+      end
+    end
+
+    context 'when log is array' do
+      it 'returns "0"' do
+        expect(subject.task3([])).to eq('0')
+      end
+    end
+
+    context 'when log is hash' do
+      it 'returns "0"' do
+        expect(subject.task3({})).to eq('0')
+      end
+    end
+
+    context 'when log is nil' do
+      it 'returns "0"' do
+        expect(subject.task3(nil)).to eq('0')
+      end
+    end
+
+    context 'when log is number' do
+      it 'returns "0"' do
+        expect(subject.task3(1)).to eq('0')
+      end
+    end
+  end
+end
diff --git a/HW03/Dmitry_Susha/spec/dmitry_susha_hw_03_t_04_spec.rb b/HW03/Dmitry_Susha/spec/dmitry_susha_hw_03_t_04_spec.rb
new file mode 100644
index 00000000..eb526080
--- /dev/null
+++ b/HW03/Dmitry_Susha/spec/dmitry_susha_hw_03_t_04_spec.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+RSpec.describe Homework3 do
+  subject { described_class.new }
+
+  describe 'task 4' do
+    context 'when log is array' do
+      it 'returns { letters: 0, digits: 0 }' do
+        expect(subject.task4([])).to eq({ letters: 0, digits: 0 })
+      end
+    end
+
+    context 'when log is hash' do
+      it 'returns { letters: 0, digits: 0 }' do
+        expect(subject.task4({})).to eq({ letters: 0, digits: 0 })
+      end
+    end
+
+    context 'when log is nil' do
+      it 'returns { letters: 0, digits: 0 }' do
+        expect(subject.task4(nil)).to eq({ letters: 0, digits: 0 })
+      end
+    end
+
+    context 'when log is number' do
+      it 'returns { letters: 0, digits: 0 }' do
+        expect(subject.task4(1)).to eq({ letters: 0, digits: 0 })
+      end
+    end
+  end
+end
diff --git a/HW03/Dmitry_Susha/spec/spec_helper.rb b/HW03/Dmitry_Susha/spec/spec_helper.rb
new file mode 100644
index 00000000..977f242c
--- /dev/null
+++ b/HW03/Dmitry_Susha/spec/spec_helper.rb
@@ -0,0 +1,105 @@
+# frozen_string_literal: true
+
+require_relative '../dmitry_susha_hw_03_t_01'
+require_relative '../dmitry_susha_hw_03_t_02'
+require_relative '../dmitry_susha_hw_03_t_03'
+require_relative '../dmitry_susha_hw_03_t_04'
+
+# This file was generated by the `rspec --init` command. Conventionally, all
+# specs live under a `spec` directory, which RSpec adds to the `$LOAD_PATH`.
+# The generated `.rspec` file contains `--require spec_helper` which will cause
+# this file to always be loaded, without a need to explicitly require it in any
+# files.
+#
+# Given that it is always loaded, you are encouraged to keep this file as
+# light-weight as possible. Requiring heavyweight dependencies from this file
+# will add to the boot time of your test suite on EVERY test run, even for an
+# individual file that may not need all of that loaded. Instead, consider making
+# a separate helper file that requires the additional dependencies and performs
+# the additional setup, and require it from the spec files that actually need
+# it.
+#
+# See http://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
+RSpec.configure do |config|
+  # rspec-expectations config goes here. You can use an alternate
+  # assertion/expectation library such as wrong or the stdlib/minitest
+  # assertions if you prefer.
+  config.expect_with :rspec do |expectations|
+    # This option will default to `true` in RSpec 4. It makes the `description`
+    # and `failure_message` of custom matchers include text for helper methods
+    # defined using `chain`, e.g.:
+    #     be_bigger_than(2).and_smaller_than(4).description
+    #     # => "be bigger than 2 and smaller than 4"
+    # ...rather than:
+    #     # => "be bigger than 2"
+    expectations.include_chain_clauses_in_custom_matcher_descriptions = true
+  end
+
+  # rspec-mocks config goes here. You can use an alternate test double
+  # library (such as bogus or mocha) by changing the `mock_with` option here.
+  config.mock_with :rspec do |mocks|
+    # Prevents you from mocking or stubbing a method that does not exist on
+    # a real object. This is generally recommended, and will default to
+    # `true` in RSpec 4.
+    mocks.verify_partial_doubles = true
+  end
+
+  # This option will default to `:apply_to_host_groups` in RSpec 4 (and will
+  # have no way to turn it off -- the option exists only for backwards
+  # compatibility in RSpec 3). It causes shared context metadata to be
+  # inherited by the metadata hash of host groups and examples, rather than
+  # triggering implicit auto-inclusion in groups with matching metadata.
+  config.shared_context_metadata_behavior = :apply_to_host_groups
+
+  # The settings below are suggested to provide a good initial experience
+  # with RSpec, but feel free to customize to your heart's content.
+  #   # This allows you to limit a spec run to individual examples or groups
+  #   # you care about by tagging them with `:focus` metadata. When nothing
+  #   # is tagged with `:focus`, all examples get run. RSpec also provides
+  #   # aliases for `it`, `describe`, and `context` that include `:focus`
+  #   # metadata: `fit`, `fdescribe` and `fcontext`, respectively.
+  #   config.filter_run_when_matching :focus
+  #
+  #   # Allows RSpec to persist some state between runs in order to support
+  #   # the `--only-failures` and `--next-failure` CLI options. We recommend
+  #   # you configure your source control system to ignore this file.
+  #   config.example_status_persistence_file_path = "spec/examples.txt"
+  #
+  #   # Limits the available syntax to the non-monkey patched syntax that is
+  #   # recommended. For more details, see:
+  #   #   - http://rspec.info/blog/2012/06/rspecs-new-expectation-syntax/
+  #   #   - http://www.teaisaweso.me/blog/2013/05/27/rspecs-new-message-expectation-syntax/
+  #   #   - http://rspec.info/blog/2014/05/notable-changes-in-rspec-3/#zero-monkey-patching-mode
+  #   config.disable_monkey_patching!
+  #
+  #   # This setting enables warnings. It's recommended, but in some cases may
+  #   # be too noisy due to issues in dependencies.
+  #   config.warnings = true
+  #
+  #   # Many RSpec users commonly either run the entire suite or an individual
+  #   # file, and it's useful to allow more verbose output when running an
+  #   # individual spec file.
+  #   if config.files_to_run.one?
+  #     # Use the documentation formatter for detailed output,
+  #     # unless a formatter has already been configured
+  #     # (e.g. via a command-line flag).
+  #     config.default_formatter = "doc"
+  #   end
+  #
+  #   # Print the 10 slowest examples and example groups at the
+  #   # end of the spec run, to help surface which specs are running
+  #   # particularly slow.
+  #   config.profile_examples = 10
+  #
+  #   # Run specs in random order to surface order dependencies. If you find an
+  #   # order dependency and want to debug it, you can fix the order by providing
+  #   # the seed, which is printed after each run.
+  #   #     --seed 1234
+  #   config.order = :random
+  #
+  #   # Seed global randomization in this process using the `--seed` CLI option.
+  #   # Setting this allows you to use `--seed` to deterministically reproduce
+  #   # test failures related to randomization by passing the same `--seed` value
+  #   # as the one that triggered the failure.
+  #   Kernel.srand config.seed
+end
diff --git a/HW04/Dmitry_Susha/.rspec b/HW04/Dmitry_Susha/.rspec
new file mode 100644
index 00000000..c99d2e73
--- /dev/null
+++ b/HW04/Dmitry_Susha/.rspec
@@ -0,0 +1 @@
+--require spec_helper
diff --git a/HW04/Dmitry_Susha/lib/student.rb b/HW04/Dmitry_Susha/lib/student.rb
index 35ab4abd..bd20db9f 100644
--- a/HW04/Dmitry_Susha/lib/student.rb
+++ b/HW04/Dmitry_Susha/lib/student.rb
@@ -14,7 +14,7 @@ def to_work!(homework)
     homework.to_work!
   end
 
-  def add_answer!(homework, answer)
+  def add_answer!(homework, answer = '')
     homework.add_answer!(answer)
   end
 
diff --git a/HW04/Dmitry_Susha/spec/file_manager_spec.rb b/HW04/Dmitry_Susha/spec/file_manager_spec.rb
new file mode 100644
index 00000000..1cc46db0
--- /dev/null
+++ b/HW04/Dmitry_Susha/spec/file_manager_spec.rb
@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+RSpec.describe FileManager do
+  let(:foo_class) { Class.new { include FileManager } }
+  let(:dir) { 'spec/helpers' }
+  let(:file_name) { 'test.txt' }
+
+  describe '.create_file' do
+    context 'when succes create file' do
+      after do
+        File.delete('spec/helpers/test.txt')
+      end
+
+      it 'creates file' do
+        expect(foo_class.new.create_file(dir, file_name)).to be_a_kind_of(File)
+      end
+    end
+  end
+
+  describe '.add_data' do
+    context 'when data present' do
+      before do
+        File.open('spec/helpers/test.txt', 'a+')
+        3.times do
+          foo_class.new.add_data(dir, file_name, '!')
+        end
+      end
+
+      after do
+        File.delete('spec/helpers/test.txt')
+      end
+
+      it 'Each line have data' do
+        File.open("#{dir}/#{file_name}", 'r').each do |line|
+          expect(line.chomp).to eq('!')
+        end
+      end
+    end
+
+    context 'when data empty' do
+      before do
+        File.open('spec/helpers/test.txt', 'a+')
+        3.times do
+          foo_class.new.add_data(dir, file_name, '')
+        end
+      end
+
+      after do
+        File.delete('spec/helpers/test.txt')
+      end
+
+      it 'Each line empty' do
+        File.open("#{dir}/#{file_name}", 'r').each do |line|
+          expect(line.chomp).to eq('')
+        end
+      end
+    end
+  end
+
+  describe '.read_dir' do
+    context 'when there is a file' do
+      before do
+        File.open('spec/helpers/test.txt', 'a+')
+      end
+
+      after do
+        File.delete('spec/helpers/test.txt')
+      end
+
+      it 'show file name' do
+        expect(foo_class.new.read_dir(dir)).to include('test.txt')
+      end
+    end
+
+    context 'when the directory is empty' do
+      it 'show array without files names' do
+        expect(foo_class.new.read_dir(dir)).to eq(['..', '.'])
+      end
+    end
+  end
+end
diff --git a/HW04/Dmitry_Susha/spec/homework_spec.rb b/HW04/Dmitry_Susha/spec/homework_spec.rb
new file mode 100644
index 00000000..db4816dd
--- /dev/null
+++ b/HW04/Dmitry_Susha/spec/homework_spec.rb
@@ -0,0 +1,114 @@
+# frozen_string_literal: true
+
+RSpec.describe Homework do
+  subject { described_class.new(title: 'title', description: 'fake', student: student) }
+
+  let(:student) { Student.new(name: 'Petr', surname: 'Petrov') }
+
+  describe '#title' do
+    it 'homework has title' do
+      expect(subject.title).to eq('title')
+    end
+  end
+
+  describe '#description' do
+    it 'homework has description' do
+      expect(subject.description).to eq('fake')
+    end
+  end
+
+  describe '#student' do
+    it 'homework has student' do
+      expect(subject.student).to eq(student)
+    end
+  end
+
+  describe '#state' do
+    it 'homework has state Created' do
+      expect(subject.state).to eq('Created')
+    end
+  end
+
+  describe '#add_homework_file' do
+    let(:homework) { described_class.new(title: 'title', description: 'fake', student: student) }
+    let(:homework_data) { 'data' }
+
+    before do
+      allow(homework).to receive(:add_data)
+    end
+
+    it 'call #add_data' do
+      homework.add_homework_file
+      expect(homework).to have_received(:add_data)
+    end
+  end
+
+  describe '#to_work!' do
+    let(:homework) { described_class.new(title: 'title', description: 'fake', student: student) }
+
+    before do
+      allow(homework).to receive_messages(update_state_in_file: 'foo', notify_mentors: 'bar')
+    end
+
+    it 'state = In work ' do
+      homework.to_work!
+      expect(homework.state).to eq('In work')
+    end
+  end
+
+  describe '#to_check!' do
+    let(:homework) { described_class.new(title: 'title', description: 'fake', student: student) }
+
+    before do
+      allow(homework).to receive_messages(update_state_in_file: 'foo', notify_mentors: 'bar')
+    end
+
+    it 'state = Pending rewiev' do
+      homework.to_check!
+      expect(homework.state).to eq('Pending rewiev')
+    end
+  end
+
+  describe '#reject!' do
+    let(:homework) { described_class.new(title: 'title', description: 'fake', student: student) }
+    let(:mentor) { 'mentor' }
+    let(:remarks) { 'remarks' }
+
+    before do
+      allow(homework).to receive_messages(update_state_in_file: 'foo', notify_students: 'bar', add_remarks: 'baz')
+    end
+
+    it 'state = Rejected' do
+      homework.reject!(mentor, remarks)
+      expect(homework.state).to eq('Rejected')
+    end
+  end
+
+  describe '#accept!' do
+    let(:homework) { described_class.new(title: 'title', description: 'fake', student: student) }
+    let(:grade) { 5 }
+
+    before do
+      allow(homework).to receive_messages(update_state_in_file: 'foo', notify_students: 'bar', add_grade: 'baz')
+    end
+
+    it 'state = Passed' do
+      homework.accept!(grade)
+      expect(homework.state).to eq('Passed')
+    end
+  end
+
+  describe '#add_answer' do
+    let(:homework) { described_class.new(title: 'title', description: 'fake', student: student) }
+    let(:answer) { 'answer' }
+
+    before do
+      allow(homework).to receive(:add_data)
+    end
+
+    it 'call #add_data' do
+      homework.add_answer!(answer)
+      expect(homework).to have_received(:add_data)
+    end
+  end
+end
diff --git a/HW04/Dmitry_Susha/spec/mentor_spec.rb b/HW04/Dmitry_Susha/spec/mentor_spec.rb
new file mode 100644
index 00000000..f7888ba8
--- /dev/null
+++ b/HW04/Dmitry_Susha/spec/mentor_spec.rb
@@ -0,0 +1,104 @@
+# frozen_string_literal: true
+
+RSpec.describe Mentor do
+  subject { described_class.new(name: 'Ivan', surname: 'Ivanov') }
+
+  let(:student) { Student.new(name: 'Petr', surname: 'Petrov') }
+  let(:homework) { Homework.new(title: 'title', description: 'fake', student: student) }
+
+  describe '#add_homework' do
+    before do
+      allow(Homework).to receive(:new).with(
+        title: 'title',
+        description: 'fake',
+        student: student
+      ).and_return('homework')
+    end
+
+    it 'create new homework' do
+      expect(subject.add_homework(title: 'title', description: 'fake', student: student)).to eq('homework')
+    end
+
+    it 'call Homework.new call' do
+      subject.add_homework(title: 'title', description: 'fake', student: student)
+      expect(Homework).to have_received(:new).with(title: 'title', description: 'fake', student: student)
+    end
+  end
+
+  describe '#invite_student_to_work' do
+    let(:mentor) { instance_double(described_class) }
+
+    before do
+      allow(mentor).to receive(:add_notification).with(homework.student)
+      allow(mentor).to receive(:invite_student_to_work).with(homework).and_return(mentor.add_notification(homework.student))
+    end
+
+    it 'call #add_notification' do
+      mentor.invite_student_to_work(homework)
+      expect(mentor).to have_received(:add_notification).with(homework.student)
+    end
+  end
+
+  describe '#subscribe_to' do
+    before do
+      allow(homework).to receive(:add_mentor_observer)
+    end
+
+    it 'call homework.add_mentor_observer' do
+      subject.subscribe_to!(homework)
+      expect(homework).to have_received(:add_mentor_observer)
+    end
+  end
+
+  describe '#reject_to_work!' do
+    context "with remarks = 'bad'" do
+      before do
+        allow(homework).to receive(:reject!).with(subject, 'bad')
+      end
+
+      it 'call homework.reject!' do
+        subject.reject_to_work!(homework, 'bad')
+        expect(homework).to have_received(:reject!).with(subject, 'bad')
+      end
+    end
+
+    context 'without remarks' do
+      before do
+        allow(homework).to receive(:reject!).with(subject, '')
+      end
+
+      it 'call homework.reject!' do
+        subject.reject_to_work!(homework)
+        expect(homework).to have_received(:reject!).with(subject, '')
+      end
+    end
+  end
+
+  describe '#accept!' do
+    context 'with default grade' do
+      before do
+        allow(homework).to receive(:accept!).with(5)
+      end
+
+      it 'call homework.reject!' do
+        subject.accept!(homework)
+        expect(homework).to have_received(:accept!).with(5)
+      end
+    end
+
+    context 'with grade = 4' do
+      before do
+        allow(homework).to receive(:accept!).with(4)
+      end
+
+      it 'call homework.reject!' do
+        subject.accept!(homework, 4)
+        expect(homework).to have_received(:accept!).with(4)
+      end
+    end
+  end
+
+  describe '#update' do
+    include_examples 'update'
+  end
+end
diff --git a/HW04/Dmitry_Susha/spec/spec_helper.rb b/HW04/Dmitry_Susha/spec/spec_helper.rb
new file mode 100644
index 00000000..a8fc78b1
--- /dev/null
+++ b/HW04/Dmitry_Susha/spec/spec_helper.rb
@@ -0,0 +1,108 @@
+# frozen_string_literal: true
+
+require_relative '../lib/file_manager'
+require_relative '../lib/homework_observable'
+require_relative '../lib/homework'
+require_relative '../lib/mentor'
+require_relative '../lib/notification'
+require_relative '../lib/student'
+require_relative '../lib/user'
+Dir['./spec/support/**/*.rb'].sort.each { |f| require f }
+# This file was generated by the `rspec --init` command. Conventionally, all
+# specs live under a `spec` directory, which RSpec adds to the `$LOAD_PATH`.
+# The generated `.rspec` file contains `--require spec_helper` which will cause
+# this file to always be loaded, without a need to explicitly require it in any
+# files.
+#
+# Given that it is always loaded, you are encouraged to keep this file as
+# light-weight as possible. Requiring heavyweight dependencies from this file
+# will add to the boot time of your test suite on EVERY test run, even for an
+# individual file that may not need all of that loaded. Instead, consider making
+# a separate helper file that requires the additional dependencies and performs
+# the additional setup, and require it from the spec files that actually need
+# it.
+#
+# See http://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
+RSpec.configure do |config|
+  # rspec-expectations config goes here. You can use an alternate
+  # assertion/expectation library such as wrong or the stdlib/minitest
+  # assertions if you prefer.
+  config.expect_with :rspec do |expectations|
+    # This option will default to `true` in RSpec 4. It makes the `description`
+    # and `failure_message` of custom matchers include text for helper methods
+    # defined using `chain`, e.g.:
+    #     be_bigger_than(2).and_smaller_than(4).description
+    #     # => "be bigger than 2 and smaller than 4"
+    # ...rather than:
+    #     # => "be bigger than 2"
+    expectations.include_chain_clauses_in_custom_matcher_descriptions = true
+  end
+
+  # rspec-mocks config goes here. You can use an alternate test double
+  # library (such as bogus or mocha) by changing the `mock_with` option here.
+  config.mock_with :rspec do |mocks|
+    # Prevents you from mocking or stubbing a method that does not exist on
+    # a real object. This is generally recommended, and will default to
+    # `true` in RSpec 4.
+    mocks.verify_partial_doubles = true
+  end
+
+  # This option will default to `:apply_to_host_groups` in RSpec 4 (and will
+  # have no way to turn it off -- the option exists only for backwards
+  # compatibility in RSpec 3). It causes shared context metadata to be
+  # inherited by the metadata hash of host groups and examples, rather than
+  # triggering implicit auto-inclusion in groups with matching metadata.
+  config.shared_context_metadata_behavior = :apply_to_host_groups
+
+  # The settings below are suggested to provide a good initial experience
+  # with RSpec, but feel free to customize to your heart's content.
+  #   # This allows you to limit a spec run to individual examples or groups
+  #   # you care about by tagging them with `:focus` metadata. When nothing
+  #   # is tagged with `:focus`, all examples get run. RSpec also provides
+  #   # aliases for `it`, `describe`, and `context` that include `:focus`
+  #   # metadata: `fit`, `fdescribe` and `fcontext`, respectively.
+  #   config.filter_run_when_matching :focus
+  #
+  #   # Allows RSpec to persist some state between runs in order to support
+  #   # the `--only-failures` and `--next-failure` CLI options. We recommend
+  #   # you configure your source control system to ignore this file.
+  #   config.example_status_persistence_file_path = "spec/examples.txt"
+  #
+  #   # Limits the available syntax to the non-monkey patched syntax that is
+  #   # recommended. For more details, see:
+  #   #   - http://rspec.info/blog/2012/06/rspecs-new-expectation-syntax/
+  #   #   - http://www.teaisaweso.me/blog/2013/05/27/rspecs-new-message-expectation-syntax/
+  #   #   - http://rspec.info/blog/2014/05/notable-changes-in-rspec-3/#zero-monkey-patching-mode
+  #   config.disable_monkey_patching!
+  #
+  #   # This setting enables warnings. It's recommended, but in some cases may
+  #   # be too noisy due to issues in dependencies.
+  #   config.warnings = true
+  #
+  #   # Many RSpec users commonly either run the entire suite or an individual
+  #   # file, and it's useful to allow more verbose output when running an
+  #   # individual spec file.
+  #   if config.files_to_run.one?
+  #     # Use the documentation formatter for detailed output,
+  #     # unless a formatter has already been configured
+  #     # (e.g. via a command-line flag).
+  #     config.default_formatter = "doc"
+  #   end
+  #
+  #   # Print the 10 slowest examples and example groups at the
+  #   # end of the spec run, to help surface which specs are running
+  #   # particularly slow.
+  #   config.profile_examples = 10
+  #
+  #   # Run specs in random order to surface order dependencies. If you find an
+  #   # order dependency and want to debug it, you can fix the order by providing
+  #   # the seed, which is printed after each run.
+  #   #     --seed 1234
+  #   config.order = :random
+  #
+  #   # Seed global randomization in this process using the `--seed` CLI option.
+  #   # Setting this allows you to use `--seed` to deterministically reproduce
+  #   # test failures related to randomization by passing the same `--seed` value
+  #   # as the one that triggered the failure.
+  #   Kernel.srand config.seed
+end
diff --git a/HW04/Dmitry_Susha/spec/student_spec.rb b/HW04/Dmitry_Susha/spec/student_spec.rb
new file mode 100644
index 00000000..65b307f2
--- /dev/null
+++ b/HW04/Dmitry_Susha/spec/student_spec.rb
@@ -0,0 +1,78 @@
+# frozen_string_literal: true
+
+RSpec.describe Student do
+  subject { described_class.new(name: 'Petr', surname: 'Petrov') }
+
+  let(:homework) { Homework.new(title: 'title', description: 'fake', student: subject) }
+
+  describe '#homeworks' do
+    let(:file_name1) { 'homework.txt' }
+    let(:user) { instance_double(described_class) }
+
+    before do
+      allow(user).to receive(:homeworks).and_return([file_name1])
+    end
+
+    it 'return file' do
+      expect(user.homeworks).to eq([file_name1])
+    end
+  end
+
+  describe '#to_work!' do
+    before do
+      allow(homework).to receive(:add_student_observer)
+      allow(homework).to receive(:to_work!)
+    end
+
+    it 'call homework.add_student_observer' do
+      subject.to_work!(homework)
+      expect(homework).to have_received(:add_student_observer)
+    end
+
+    it 'call homework.to_work!' do
+      subject.to_work!(homework)
+      expect(homework).to have_received(:to_work!)
+    end
+  end
+
+  describe '#add_answer!' do
+    context "with answer = 'i dont know'" do
+      before do
+        allow(homework).to receive(:add_answer!).with('i dont know')
+      end
+
+      it 'call homework.add_answer! call' do
+        subject.add_answer!(homework, 'i dont know')
+        expect(homework).to have_received(:add_answer!).with('i dont know')
+      end
+    end
+
+    context 'without answer' do
+      before do
+        allow(homework).to receive(:add_answer!)
+      end
+
+      it 'call homework.add_answer!' do
+        subject.add_answer!(homework)
+        expect(homework).to have_received(:add_answer!)
+      end
+    end
+  end
+
+  describe '#to_check!' do
+    context "with answer = 'i dont know'" do
+      before do
+        allow(homework).to receive(:to_check!)
+      end
+
+      it 'call homework.to_check!' do
+        subject.to_check!(homework)
+        expect(homework).to have_received(:to_check!)
+      end
+    end
+  end
+
+  describe '#update' do
+    include_examples 'update'
+  end
+end
diff --git a/HW04/Dmitry_Susha/spec/support/sharred_examples/shared_example_for_update.rb b/HW04/Dmitry_Susha/spec/support/sharred_examples/shared_example_for_update.rb
new file mode 100644
index 00000000..0c25ef62
--- /dev/null
+++ b/HW04/Dmitry_Susha/spec/support/sharred_examples/shared_example_for_update.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+RSpec.shared_examples 'update' do
+  describe '#update' do
+    let(:student) { Student.new(name: 'Petr', surname: 'Petrov') }
+    let(:homework) { Homework.new(title: 'title', description: 'fake', student: student) }
+    let(:user) { described_class.new(name: 'name', surname: 'surname') }
+
+    before do
+      allow(user).to receive(:add_notification)
+    end
+
+    it 'wait #add_notification with arguments' do
+      user.update(homework)
+      expect(user).to have_received(:add_notification)
+    end
+  end
+end
diff --git a/HW04/Dmitry_Susha/spec/user_spec.rb b/HW04/Dmitry_Susha/spec/user_spec.rb
new file mode 100644
index 00000000..9b58df65
--- /dev/null
+++ b/HW04/Dmitry_Susha/spec/user_spec.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+RSpec.describe User do
+  subject { described_class.new(name: 'Ivan', surname: 'Ivanov') }
+
+  describe '#name' do
+    it 'user has name' do
+      expect(subject.name).to eq('Ivan')
+    end
+  end
+
+  describe '#surname' do
+    it 'user has surname' do
+      expect(subject.surname).to eq('Ivanov')
+    end
+  end
+end