diff --git a/spec/daru/io/exporters/avro_spec.rb b/spec/daru/io/exporters/avro_spec.rb
index d99b549..85ee358 100644
--- a/spec/daru/io/exporters/avro_spec.rb
+++ b/spec/daru/io/exporters/avro_spec.rb
@@ -8,13 +8,13 @@
     )
   end
 
-  include_context 'exporter setup'
+  include_context 'with exporter setup'
 
   let(:filename) { 'test.avro' }
 
   before { described_class.new(df, schema).write(tempfile.path) }
 
-  context 'writes DataFrame to an Avro file' do
+  context 'when writes DataFrame to an Avro file' do
     context 'when schema is Hash' do
       let(:schema) do
         {
diff --git a/spec/daru/io/exporters/csv_spec.rb b/spec/daru/io/exporters/csv_spec.rb
index e3dad6b..c3dfc69 100644
--- a/spec/daru/io/exporters/csv_spec.rb
+++ b/spec/daru/io/exporters/csv_spec.rb
@@ -1,13 +1,13 @@
 RSpec.describe Daru::IO::Exporters::CSV do
   subject { File.open(tempfile.path, &:readline).chomp.split(',', -1) }
 
-  include_context 'exporter setup'
+  include_context 'with exporter setup'
 
   let(:filename) { 'test.csv' }
 
   before { described_class.new(df, opts).write(tempfile.path) }
 
-  context 'writes DataFrame to a CSV file' do
+  context 'when writes DataFrame to a CSV file' do
     subject { Daru::DataFrame.rows content[1..-1].map { |x| x.map { |y| convert(y) } }, order: content[0] }
 
     let(:opts) { {} }
@@ -25,12 +25,12 @@
       ]
   end
 
-  context 'writes headers unless headers=false' do
+  context 'when writes headers unless headers=false' do
     it { is_expected.to be_an(Array) }
     it { is_expected.to eq(df.vectors.to_a) }
   end
 
-  context 'does not write headers when headers=false' do
+  context 'when does not write headers when headers=false' do
     let(:headers) { false              }
     let(:opts)    { {headers: headers} }
 
@@ -38,7 +38,7 @@
     it { is_expected.to eq(df.head(1).map { |v| (v.first || '').to_s }) }
   end
 
-  context 'writes convert_comma only on float values' do
+  context 'when writes convert_comma only on float values' do
     subject { CSV.read(tempfile.path, col_sep: ';') }
 
     let(:df)      { Daru::DataFrame.new('a' => [1, 4.4, nil, 'Sr. Arthur']) }
@@ -47,7 +47,7 @@
     it { is_expected.to eq([['a'], ['1'], ['4,4'], [''], ['Sr. Arthur']]) }
   end
 
-  context 'writes into .csv.gz format' do
+  context 'when writes into .csv.gz format' do
     subject        { Zlib::GzipReader.new(open(tempfile.path)).read.split("\n") }
 
     let(:opts)     { {compression: :gzip} }
@@ -57,7 +57,7 @@
     it { is_expected.to eq(['a,b,c,d', '1,11,a,', '2,22,g,23', '3,33,4,4', '4,44,5,a', '5,55,addadf,ff']) }
   end
 
-  context 'writes into .csv.gz format with only order' do
+  context 'when writes into .csv.gz format with only order' do
     subject        { Zlib::GzipReader.new(open(tempfile.path)).read.split("\n") }
 
     let(:df)       { Daru::DataFrame.new('a' => [], 'b' => [], 'c' => [], 'd' => []) }
diff --git a/spec/daru/io/exporters/excel_spec.rb b/spec/daru/io/exporters/excel_spec.rb
index eacc037..ab3d8a6 100644
--- a/spec/daru/io/exporters/excel_spec.rb
+++ b/spec/daru/io/exporters/excel_spec.rb
@@ -1,5 +1,5 @@
 RSpec.describe Daru::IO::Exporters::Excel do
-  include_context 'exporter setup'
+  include_context 'with exporter setup'
 
   let(:filename) { 'test_write.xls' }
   let(:content)  { Spreadsheet.open tempfile.path }
@@ -7,7 +7,7 @@
 
   before { described_class.new(df, **opts).write(tempfile.path) }
 
-  context 'writes to excel spreadsheet' do
+  context 'when writes to excel spreadsheet' do
     subject do
       Daru::DataFrame.rows(
         Spreadsheet.open(tempfile.path).worksheet(0).rows[1..-1].map(&:to_a),
@@ -29,25 +29,25 @@
       ]
   end
 
-  context 'writes to excel spreadsheet with header formatting' do
+  context 'when writes to excel spreadsheet with header formatting' do
     subject { Spreadsheet.open(tempfile.path).worksheet(0).rows[0].format(0).font.color }
 
     it { is_expected.to eq(:blue) }
   end
 
-  context 'writes to excel spreadsheet with index formatting' do
+  context 'when writes to excel spreadsheet with index formatting' do
     subject { Spreadsheet.open(tempfile.path).worksheet(0).rows[1].format(0).font.color }
 
     it { is_expected.to eq(:green) }
   end
 
-  context 'writes to excel spreadsheet with data formatting' do
+  context 'when writes to excel spreadsheet with data formatting' do
     subject { Spreadsheet.open(tempfile.path).worksheet(0).rows[1].format(1).font.color }
 
     it { is_expected.to eq(:red) }
   end
 
-  context 'writes to excel spreadsheet with multi-index' do
+  context 'when writes to excel spreadsheet with multi-index' do
     subject { Spreadsheet.open(tempfile.path).worksheet(0).rows }
 
     let(:df) do
diff --git a/spec/daru/io/exporters/json_spec.rb b/spec/daru/io/exporters/json_spec.rb
index f272218..45e972f 100644
--- a/spec/daru/io/exporters/json_spec.rb
+++ b/spec/daru/io/exporters/json_spec.rb
@@ -1,5 +1,5 @@
 RSpec.describe Daru::IO::Exporters::JSON do
-  include_context 'exporter setup'
+  include_context 'with exporter setup'
 
   subject { JSON.parse(File.read(tempfile.path)) }
 
@@ -21,13 +21,13 @@
 
   before { described_class.new(df, pretty: pretty, orient: orient, **opts).write(tempfile.path) }
 
-  context 'writes DataFrame with default jsonpath options' do
+  context 'when writes DataFrame with default jsonpath options' do
     it                { is_expected.to be_an(Array).and all be_a(Hash) }
     its(:count)       { is_expected.to eq(3)                           }
     its('first.keys') { is_expected.to match_array(%w[name age sex])   }
   end
 
-  context 'writes DataFrame with orient: :values' do
+  context 'when writes DataFrame with orient: :values' do
     let(:orient) { :values }
 
     it          { is_expected.to be_an(Array).and all be_an(Array)                     }
@@ -35,7 +35,7 @@
     its(:first) { is_expected.to eq(['Jon Snow', 'Rhaegar Targaryen', 'Lyanna Stark']) }
   end
 
-  context 'writes DataFrame with orient: :split' do
+  context 'when writes DataFrame with orient: :split' do
     let(:orient) { :split }
 
     it          { is_expected.to be_a(Hash).and all be_an(Array) }
@@ -43,7 +43,7 @@
     its(:keys)  { is_expected.to eq(%w[vectors index data])      }
   end
 
-  context 'writes DataFrame with orient: :index' do
+  context 'when writes DataFrame with orient: :index' do
     let(:orient) { :index }
 
     it          { is_expected.to be_an(Array).and all be_a(Hash)                                     }
@@ -51,7 +51,7 @@
     its(:first) { is_expected.to eq('child' => {'sex' => 'Male', 'age' => 18, 'name' => 'Jon Snow'}) }
   end
 
-  context 'writes DataFrame with nested jsonpath options' do
+  context 'when writes DataFrame with nested jsonpath options' do
     let(:opts) { {name: '$.person.name', age: '$.person.age', sex: '$.gender', index: '$.relation'} }
 
     it { is_expected.to be_an(Array).and all be_a(Hash) }
@@ -64,14 +64,14 @@
     end
   end
 
-  context 'writes DataFrame with dynamic jsonpath options' do
+  context 'when writes DataFrame with dynamic jsonpath options' do
     let(:opts) { {age: '$.{index}.{name}.age', sex: '$.{index}.{name}.gender'} }
 
     it { is_expected.to be_an(Array).and all be_a(Hash) }
     its(:first) { is_expected.to eq('child' => {'Jon Snow' => {'age' => 18, 'gender' => 'Male'}}) }
   end
 
-  context 'writes DataFrame with block manipulation' do
+  context 'when writes DataFrame with block manipulation' do
     before do
       described_class.new(df, orient: orient, pretty: pretty) do |json|
         json.map { |j| [j.keys.first, j.values.first] }.to_h
diff --git a/spec/daru/io/exporters/r_data_spec.rb b/spec/daru/io/exporters/r_data_spec.rb
index 60da5d6..25e49f4 100644
--- a/spec/daru/io/exporters/r_data_spec.rb
+++ b/spec/daru/io/exporters/r_data_spec.rb
@@ -1,7 +1,7 @@
 RSpec.describe Daru::IO::Exporters::RData do
   subject { Daru::DataFrame.new(instance.send(variables[0].to_sym)) }
 
-  include_context 'exporter setup'
+  include_context 'with exporter setup'
 
   let(:instance)  { RSRuby.instance                             }
   let(:filename)  { 'test.RData'                                }
@@ -9,8 +9,8 @@
 
   before { described_class.new(**opts).write(tempfile.path) }
 
-  context 'writes DataFrame to a RData file' do
-    let(:opts)    { {:'first.df' => df, :'last.df' => df} }
+  context 'when writes DataFrame to a RData file' do
+    let(:opts) { {:'first.df' => df, :'last.df' => df} }
 
     it_behaves_like 'exact daru dataframe',
       ncols: 4,
diff --git a/spec/daru/io/exporters/rds_spec.rb b/spec/daru/io/exporters/rds_spec.rb
index 570aa1e..ed0589c 100644
--- a/spec/daru/io/exporters/rds_spec.rb
+++ b/spec/daru/io/exporters/rds_spec.rb
@@ -1,14 +1,14 @@
 RSpec.describe Daru::IO::Exporters::RDS do
   subject { Daru::DataFrame.new(RSRuby.instance.eval_R("readRDS('#{tempfile.path}')")) }
 
-  include_context 'exporter setup'
+  include_context 'with exporter setup'
 
   let(:variable) { 'test.dataframe' }
   let(:filename) { 'test.rds'       }
 
   before { described_class.new(df, variable).write(tempfile.path) }
 
-  context 'writes DataFrame to a RDS file' do
+  context 'when writes DataFrame to a RDS file' do
     it_behaves_like 'exact daru dataframe',
       ncols: 4,
       nrows: 5,
diff --git a/spec/daru/io/exporters/sql_spec.rb b/spec/daru/io/exporters/sql_spec.rb
index c38a239..c086a39 100644
--- a/spec/daru/io/exporters/sql_spec.rb
+++ b/spec/daru/io/exporters/sql_spec.rb
@@ -1,5 +1,5 @@
 RSpec.describe Daru::IO::Exporters::SQL do
-  include_context 'exporter setup'
+  include_context 'with exporter setup'
 
   let(:dbh)            { double }
   let(:table)          { 'test' }
diff --git a/spec/daru/io/importers/active_record_spec.rb b/spec/daru/io/importers/active_record_spec.rb
index 11e2d32..f843e12 100644
--- a/spec/daru/io/importers/active_record_spec.rb
+++ b/spec/daru/io/importers/active_record_spec.rb
@@ -1,5 +1,6 @@
 RSpec.describe Daru::IO::Importers::ActiveRecord do
-  include_context 'sqlite3 database setup'
+  include_context 'with sqlite3 database setup'
+
   context 'without specifying field names' do
     let(:fields) { [] }
 
diff --git a/spec/daru/io/importers/avro_spec.rb b/spec/daru/io/importers/avro_spec.rb
index c36d4ac..8c3ffc2 100644
--- a/spec/daru/io/importers/avro_spec.rb
+++ b/spec/daru/io/importers/avro_spec.rb
@@ -3,7 +3,7 @@
 
   let(:path) { '' }
 
-  context 'on complex numbers avro file' do
+  context 'when on complex numbers avro file' do
     let(:path) { 'spec/fixtures/avro/one_complex.avro' }
 
     it_behaves_like 'exact daru dataframe',
@@ -13,7 +13,7 @@
       data: [[100],[200]]
   end
 
-  context 'on twitter avro file' do
+  context 'when on twitter avro file' do
     let(:path) { 'spec/fixtures/avro/twitter.avro' }
 
     it_behaves_like 'exact daru dataframe',
@@ -41,7 +41,7 @@
       ]
   end
 
-  context 'on users avro file' do
+  context 'when on users avro file' do
     let(:path) { 'spec/fixtures/avro/users.avro' }
 
     it_behaves_like 'exact daru dataframe',
diff --git a/spec/daru/io/importers/csv_spec.rb b/spec/daru/io/importers/csv_spec.rb
index 1d28cdc..44064c5 100644
--- a/spec/daru/io/importers/csv_spec.rb
+++ b/spec/daru/io/importers/csv_spec.rb
@@ -18,7 +18,7 @@
   let(:path) { 'spec/fixtures/csv/matrix_test.csv' }
   let(:opts) { {col_sep: ' ', headers: true}       }
 
-  context 'loads from a CSV file' do
+  context 'when loads from a CSV file' do
     let('subject.vectors') { %I[image_resolution mls true_transform].to_index }
 
     it_behaves_like 'exact daru dataframe',
@@ -31,7 +31,7 @@
                                    ',-0.3027024,4262.65,0,0,0,1'
   end
 
-  context 'works properly for repeated headers' do
+  context 'when works properly for repeated headers' do
     let(:path)  { 'spec/fixtures/csv/repeated_fields.csv' }
     let(:opts)  { {header_converters: :symbol}            }
 
@@ -42,7 +42,7 @@
       age_2: Daru::Vector.new([3, 4, 5, 6, nil, 8])
   end
 
-  context 'accepts scientific notation as float' do
+  context 'when accepts scientific notation as float' do
     let(:path) { 'spec/fixtures/csv/scientific_notation.csv' }
     let(:opts) { {order: %w[x y]}                            }
     let(:df)   { subject                                     }
@@ -64,7 +64,7 @@
     end
   end
 
-  context 'follows the order of columns given in CSV' do
+  context 'when follows the order of columns given in CSV' do
     let(:path)  { 'spec/fixtures/csv/sales-funnel.csv' }
     let(:opts)  { {}                                   }
 
@@ -74,7 +74,7 @@
       order: %w[Account Name Rep Manager Product Quantity Price Status]
   end
 
-  context 'parses empty dataframe from CSV with only headers' do
+  context 'when parses empty dataframe from CSV with only headers' do
     let(:path)  { 'spec/fixtures/csv/column_headers_only.csv' }
     let(:opts)  { {} }
 
@@ -84,7 +84,7 @@
       order: %w[col0 col1 col2]
   end
 
-  context 'skips rows from CSV files with headers option' do
+  context 'when skips rows from CSV files with headers option' do
     let(:path)  { 'spec/fixtures/csv/sales-funnel.csv' }
     let(:opts)  { {skiprows: 8, headers: true} }
 
@@ -94,7 +94,7 @@
       order: %i[account manager name price product quantity rep status]
   end
 
-  context 'skips rows from CSV files without headers option' do
+  context 'when skips rows from CSV files without headers option' do
     let(:path)  { 'spec/fixtures/csv/sales-funnel.csv' }
     let(:opts)  { {skiprows: 8} }
 
@@ -104,7 +104,7 @@
       order: %w[Account Name Rep Manager Product Quantity Price Status]
   end
 
-  context 'checks for boolean converter' do
+  context 'when checks for boolean converter' do
     let(:path) { 'spec/fixtures/csv/boolean_converter_test.csv' }
     let(:opts) { {converters: [:boolean]} }
 
@@ -114,7 +114,7 @@
     its('Domestic.to_a') { is_expected.to all be_boolean }
   end
 
-  context 'checks for skip_blanks option to skip empty rows' do
+  context 'when checks for skip_blanks option to skip empty rows' do
     let(:path) { 'spec/fixtures/csv/empty_rows_test.csv' }
 
     it_behaves_like 'exact daru dataframe',
@@ -122,7 +122,7 @@
       nrows: 13
   end
 
-  context 'checks for equal parsing of csv and csv.gz files' do
+  context 'when checks for equal parsing of csv and csv.gz files' do
     ALL_CSV_FILES.each do |file|
       before { Zlib::GzipWriter.open(path) { |gz| gz.write File.read(csv_path) } }
 
@@ -137,7 +137,7 @@
     end
   end
 
-  context 'checks for equal parsing of local CSV files and remote CSV files' do
+  context 'when checks for equal parsing of local CSV files and remote CSV files' do
     ALL_CSV_FILES.each do |file|
       let(:local) { described_class.read("spec/fixtures/csv/#{file}.csv").call }
       let(:path)  { "http://dummy-remote-url/#{file}.csv"                      }
diff --git a/spec/daru/io/importers/excel_spec.rb b/spec/daru/io/importers/excel_spec.rb
index 579a0db..528c08e 100644
--- a/spec/daru/io/importers/excel_spec.rb
+++ b/spec/daru/io/importers/excel_spec.rb
@@ -1,5 +1,5 @@
 RSpec.describe Daru::IO::Importers::Excel do
-  context 'loads from excel spreadsheet' do
+  context 'when loads from excel spreadsheet' do
     subject    { described_class.read(path).call }
 
     let(:path) { 'spec/fixtures/excel/test_xls.xls' }
diff --git a/spec/daru/io/importers/excelx_spec.rb b/spec/daru/io/importers/excelx_spec.rb
index eb09208..7cee491 100644
--- a/spec/daru/io/importers/excelx_spec.rb
+++ b/spec/daru/io/importers/excelx_spec.rb
@@ -61,7 +61,7 @@
     end
   end
 
-  context 'checks for equal parsing of local XLSX files and remote XLSX files' do
+  context 'when checks for equal parsing of local XLSX files and remote XLSX files' do
     %w[LOBSTAHS_rt.windows Microcode Stock-counts-sheet].each do |file|
       let(:local) { described_class.read("spec/fixtures/excelx/#{file}.xlsx").call }
       let(:path)  { "http://dummy-remote-url/#{file}.xlsx" }
diff --git a/spec/daru/io/importers/html_spec.rb b/spec/daru/io/importers/html_spec.rb
index 042c7ef..f76f32e 100644
--- a/spec/daru/io/importers/html_spec.rb
+++ b/spec/daru/io/importers/html_spec.rb
@@ -4,13 +4,13 @@
   let(:opts)     { {} }
   let(:df_index) { 0  }
 
-  context 'in wiki info table' do
+  context 'when in wiki info table' do
     let(:path)  { 'spec/fixtures/html/wiki_table_info.html' }
     let(:order) { %w[FName LName Age]                       }
     let(:index) { %w[One Two Three Four Five Six Seven]     }
     let(:name)  { 'Wikipedia Information Table'             }
 
-    context 'returns default dataframe' do
+    context 'when returns default dataframe' do
       it_behaves_like 'exact daru dataframe',
         ncols: 3,
         nrows: 7,
@@ -22,7 +22,7 @@
         ]
     end
 
-    context 'returns user-modified dataframe' do
+    context 'when returns user-modified dataframe' do
       let(:opts) { {order: order, index: index, name: name} }
 
       it_behaves_like 'exact daru dataframe',
@@ -39,10 +39,10 @@
     end
   end
 
-  context 'in wiki climate data' do
+  context 'when in wiki climate data' do
     let(:path) { 'spec/fixtures/html/wiki_climate.html' }
 
-    context 'returns default dataframe' do
+    context 'when returns default dataframe' do
       it_behaves_like 'exact daru dataframe',
         ncols: 13,
         nrows: 10,
@@ -62,7 +62,7 @@
     let(:index) { %w[W X Y Z]                            }
     let(:name)  { 'Small HTML table with index'          }
 
-    context 'returns user-modified dataframe' do
+    context 'when returns user-modified dataframe' do
       let(:opts) { {index: index, name: name} }
 
       it_behaves_like 'exact daru dataframe',
@@ -75,12 +75,12 @@
     end
   end
 
-  context 'in year-wise passengers figure' do
+  context 'when in year-wise passengers figure' do
     let(:path)  { 'spec/fixtures/html/macau.html' }
     let(:match) { '2001'                          }
     let(:name)  { 'Year-wise Passengers Figure'   }
 
-    context 'returns matching dataframes with index' do
+    context 'when returns matching dataframes with index' do
       let(:opts) { {match: match, name: name} }
 
       it_behaves_like 'exact daru dataframe',
@@ -107,13 +107,13 @@
     end
   end
 
-  context 'in share market data' do
+  context 'when in share market data' do
     let(:path)  { 'spec/fixtures/html/moneycontrol.html' }
     let(:match) { 'Sun Pharma'                           }
     let(:index) { %w[Alpha Beta Gamma Delta Misc]        }
     let(:name)  { 'Share Market Analysis' }
 
-    context 'returns matching dataframes' do
+    context 'when returns matching dataframes' do
       let(:opts) { {match: match} }
 
       it_behaves_like 'exact daru dataframe',
@@ -129,7 +129,7 @@
         ].transpose
     end
 
-    context 'returns user-modified matching dataframes' do
+    context 'when returns user-modified matching dataframes' do
       let(:opts) { {match: match, index: index, name: name} }
 
       it_behaves_like 'exact daru dataframe',
@@ -148,10 +148,10 @@
     end
   end
 
-  context 'in election results data' do
+  context 'when in election results data' do
     let(:path) { 'spec/fixtures/html/eciresults.html' }
 
-    context 'returns default dataframes' do
+    context 'when returns default dataframes' do
       it_behaves_like 'exact daru dataframe',
         ncols: 2,
         nrows: 19,
diff --git a/spec/daru/io/importers/json_spec.rb b/spec/daru/io/importers/json_spec.rb
index ad5a559..77b65aa 100644
--- a/spec/daru/io/importers/json_spec.rb
+++ b/spec/daru/io/importers/json_spec.rb
@@ -7,8 +7,8 @@
   let(:columns)       { nil }
   let(:named_columns) { {}  }
 
-  context 'on simple json file' do
-    context 'in NASA data' do
+  context 'when on simple json file' do
+    context 'when in NASA data' do
       let(:path) { 'spec/fixtures/json/nasadata.json' }
 
       context 'without xpath (simple json)' do
@@ -22,7 +22,7 @@
 
   it_behaves_like 'importer with json-path option'
 
-  context 'parses json response' do
+  context 'when parses json response' do
     subject { described_class.from(instance).call(*columns, order: order, index: index, **named_columns) }
 
     let(:instance) { ::JSON.parse(File.read('spec/fixtures/json/nasadata.json')) }
@@ -33,7 +33,7 @@
       order: %w[designation discovery_date h_mag i_deg moid_au orbit_class period_yr pha q_au_1 q_au_2]
   end
 
-  context 'parses json string' do
+  context 'when parses json string' do
     subject { described_class.from(instance).call(*columns, order: order, index: index, **named_columns) }
 
     let(:instance) { File.read('spec/fixtures/json/nasadata.json') }
@@ -44,7 +44,7 @@
       order: %w[designation discovery_date h_mag i_deg moid_au orbit_class period_yr pha q_au_1 q_au_2]
   end
 
-  context 'parses remote and local file similarly' do
+  context 'when parses remote and local file similarly' do
     let(:local_path) { 'spec/fixtures/json/nasadata.json'      }
     let(:path)       { 'http://dummy-remote-url/nasadata.json' }
 
@@ -61,8 +61,8 @@
       order: %w[designation discovery_date h_mag i_deg moid_au orbit_class period_yr pha q_au_1 q_au_2]
   end
 
-  context 'raises error for invalid argument' do # rubocop:disable RSpec/EmptyExampleGroup
-    context 'json input is invalid' do # rubocop:disable RSpec/EmptyExampleGroup
+  context 'when raises error for invalid argument' do # rubocop:disable RSpec/EmptyExampleGroup
+    context 'when json input is invalid' do # rubocop:disable RSpec/EmptyExampleGroup
       subject { described_class.from([]).call(*columns, order: order, index: index, **named_columns) }
 
       let(:order)         { %i[a b] }
diff --git a/spec/daru/io/importers/mongo_spec.rb b/spec/daru/io/importers/mongo_spec.rb
index 986aa6e..f5fb578 100644
--- a/spec/daru/io/importers/mongo_spec.rb
+++ b/spec/daru/io/importers/mongo_spec.rb
@@ -45,8 +45,8 @@ def store(path)
     before { store path                  }
     after  { connection[collection].drop }
 
-    context 'on simple json file' do
-      context 'in NASA data' do
+    context 'when on simple json file' do
+      context 'when in NASA data' do
         let(:path) { 'spec/fixtures/json/nasadata.json' }
         let(:vector) do
           %w[_id designation discovery_date h_mag i_deg moid_au orbit_class period_yr pha q_au_1 q_au_2]
@@ -59,7 +59,7 @@ def store(path)
           its('vectors.to_a') { is_expected.to match_array(vector) }
         end
 
-        context 'fetches paginated results - first page' do
+        context 'when fetches paginated results - first page' do
           let(:limit)      { 30 }
           let(:nrows)      { 30 }
 
@@ -70,7 +70,7 @@ def store(path)
           its('vectors.to_a') { is_expected.to match_array(vector) }
         end
 
-        context 'fetches paginated results - last page' do
+        context 'when fetches paginated results - last page' do
           let(:skip)       { 180 }
           let(:limit)      { 30  }
 
@@ -80,7 +80,7 @@ def store(path)
           its('vectors.to_a') { is_expected.to match_array(vector) }
         end
 
-        context 'fetches results with filter' do
+        context 'when fetches results with filter' do
           let(:filter)     { {pha: :N} }
           let(:limit)      { 200       }
 
@@ -90,7 +90,7 @@ def store(path)
           its('vectors.to_a') { is_expected.to match_array(vector) }
         end
 
-        context 'fetches results with filter and pagination' do
+        context 'when fetches results with filter and pagination' do
           let(:filter)     { {pha: :N} }
           let(:limit)      { 100       }
 
diff --git a/spec/daru/io/importers/plaintext_spec.rb b/spec/daru/io/importers/plaintext_spec.rb
index 09d0f30..738c1ea 100644
--- a/spec/daru/io/importers/plaintext_spec.rb
+++ b/spec/daru/io/importers/plaintext_spec.rb
@@ -3,7 +3,7 @@
 
   let(:vectors) { %i[v1 v2 v3] }
 
-  context 'reads data from plain text files' do
+  context 'when reads data from plain text files' do
     let(:path)    { 'spec/fixtures/plaintext/bank2.dat' }
     let(:vectors) { %i[v1 v2 v3 v4 v5 v6] }
 
@@ -13,7 +13,7 @@
       order: %i[v1 v2 v3 v4 v5 v6]
   end
 
-  context 'understands empty fields', skip: 'See FIXME note at importers/plainext.rb#L33-L36' do
+  context 'when understands empty fields', skip: 'See FIXME note at importers/plainext.rb#L33-L36' do
     let(:path) { 'spec/fixtures/plaintext/empties.dat' }
 
     it_behaves_like 'exact daru dataframe',
@@ -22,7 +22,7 @@
       :'row[1].to_a' => [4, nil, 6]
   end
 
-  context 'understands non-numeric fields' do
+  context 'when understands non-numeric fields' do
     let(:path) { 'spec/fixtures/plaintext/strings.dat' }
 
     it_behaves_like 'exact daru dataframe',
diff --git a/spec/daru/io/importers/r_data_spec.rb b/spec/daru/io/importers/r_data_spec.rb
index c51e08e..e3f71b7 100644
--- a/spec/daru/io/importers/r_data_spec.rb
+++ b/spec/daru/io/importers/r_data_spec.rb
@@ -3,7 +3,7 @@
 
   let(:variable) { nil }
 
-  context 'reads data from ACScounty file' do
+  context 'when reads data from ACScounty file' do
     let(:path)     { 'spec/fixtures/rdata/ACScounty.RData' }
     let(:variable) { 'ACS3'                                }
 
@@ -20,7 +20,7 @@
       ]
   end
 
-  context 'reads data from Filings-by-state file' do
+  context 'when reads data from Filings-by-state file' do
     let(:path)     { 'spec/fixtures/rdata/Filings-by-state.RData' }
     let(:variable) { 'bk.rates'                                   }
 
@@ -33,7 +33,7 @@
       ]
   end
 
-  context 'reads data from Ownership file' do
+  context 'when reads data from Ownership file' do
     let(:path)     { 'spec/fixtures/rdata/Ownership.RData' }
     let(:variable) { 'ownership.state.qtr'                 }
 
diff --git a/spec/daru/io/importers/rds_spec.rb b/spec/daru/io/importers/rds_spec.rb
index ad6dfde..3a21baf 100644
--- a/spec/daru/io/importers/rds_spec.rb
+++ b/spec/daru/io/importers/rds_spec.rb
@@ -1,7 +1,7 @@
 RSpec.describe Daru::IO::Importers::RDS do
   subject { described_class.read(path).call }
 
-  context 'reads data from bc_sites RDS file' do
+  context 'when reads data from bc_sites RDS file' do
     let(:path) { 'spec/fixtures/rds/bc_sites.rds' }
 
     it_behaves_like 'exact daru dataframe',
@@ -16,7 +16,7 @@
       ]
   end
 
-  context 'reads data from chicago RDS file' do
+  context 'when reads data from chicago RDS file' do
     let(:path) { 'spec/fixtures/rds/chicago.rds' }
 
     it_behaves_like 'exact daru dataframe',
@@ -28,7 +28,7 @@
       ]
   end
 
-  context 'reads data from healthexp RDS file' do
+  context 'when reads data from healthexp RDS file' do
     let(:path) { 'spec/fixtures/rds/healthexp.Rds' }
 
     it_behaves_like 'exact daru dataframe',
@@ -40,7 +40,7 @@
       ]
   end
 
-  context 'reads data from heights RDS file' do
+  context 'when reads data from heights RDS file' do
     let(:path) { 'spec/fixtures/rds/heights.RDS' }
 
     it_behaves_like 'exact daru dataframe',
@@ -52,7 +52,7 @@
       ]
   end
 
-  context 'reads data from maacs_env RDS file' do
+  context 'when reads data from maacs_env RDS file' do
     let(:path) { 'spec/fixtures/rds/maacs_env.rds' }
 
     it_behaves_like 'exact daru dataframe',
@@ -66,7 +66,7 @@
       ]
   end
 
-  context 'reads data from RPPdataConverted RDS file' do
+  context 'when reads data from RPPdataConverted RDS file' do
     let(:path) { 'spec/fixtures/rds/RPPdataConverted.rds' }
 
     it_behaves_like 'exact daru dataframe',
diff --git a/spec/daru/io/importers/redis_spec.rb b/spec/daru/io/importers/redis_spec.rb
index f160654..8c6a19e 100644
--- a/spec/daru/io/importers/redis_spec.rb
+++ b/spec/daru/io/importers/redis_spec.rb
@@ -48,7 +48,7 @@ def store(key, value)
 
   after { connection.flushdb }
 
-  context 'on array of keys having hashes' do
+  context 'when on array of keys having hashes' do
     let(:index) { %i[10001 10002 10003 10004] }
     let(:data) do
       [
@@ -88,7 +88,7 @@ def store(key, value)
     end
   end
 
-  context 'on keys having array of hashes' do
+  context 'when on keys having array of hashes' do
     let(:index) { %i[10001 10003] }
     let(:data) do
       [
@@ -126,7 +126,7 @@ def store(key, value)
     end
   end
 
-  context 'on hash keys having arrays' do
+  context 'when on hash keys having arrays' do
     let(:index) { %i[age living name] }
     let(:data) do
       [
@@ -160,7 +160,7 @@ def store(key, value)
     end
   end
 
-  context 'on timestamps' do
+  context 'when on timestamps' do
     let(:index) { %i[090620171216 090620171218 090620171222 100620171225] }
     let(:data) do
       [
@@ -171,7 +171,7 @@ def store(key, value)
       ]
     end
 
-    context 'gets keys with pattern match and count' do
+    context 'when gets keys with pattern match and count' do
       let(:count)   { 3           }
       let(:pattern) { '09062017*' }
 
@@ -187,7 +187,7 @@ def store(key, value)
         ]
     end
 
-    context 'gets keys without pattern and count' do
+    context 'when gets keys without pattern and count' do
       it_behaves_like 'unordered daru dataframe',
         nrows: 4,
         ncols: 2,
@@ -201,7 +201,7 @@ def store(key, value)
         ]
     end
 
-    context 'gets keys with pattern match' do
+    context 'when gets keys with pattern match' do
       let(:pattern) { '09062017*' }
 
       it_behaves_like 'unordered daru dataframe',
@@ -217,12 +217,12 @@ def store(key, value)
     end
   end
 
-  context 'on dummy data of paginated keys' do
+  context 'when on dummy data of paginated keys' do
     let(:data)    { Array.new(2000) { |i| {a: "a#{i}", b: "b#{i}"} } }
     let(:index)   { Array.new(2000) { |i| "key#{i}".to_sym }         }
     let(:pattern) { 'key1*'                                          }
 
-    context 'parses only 1st page by default' do
+    context 'when parses only 1st page by default' do
       let(:count) { 400 }
 
       it_behaves_like 'unordered daru dataframe',
@@ -231,7 +231,7 @@ def store(key, value)
         order: %i[a b]
     end
 
-    context 'parses entire pagination' do
+    context 'when parses entire pagination' do
       let(:count) { nil }
 
       it_behaves_like 'unordered daru dataframe',
diff --git a/spec/daru/io/importers/sql_spec.rb b/spec/daru/io/importers/sql_spec.rb
index 2884602..cfd848a 100644
--- a/spec/daru/io/importers/sql_spec.rb
+++ b/spec/daru/io/importers/sql_spec.rb
@@ -1,5 +1,5 @@
 RSpec.describe Daru::IO::Importers::SQL do
-  include_context 'sqlite3 database setup'
+  include_context 'with sqlite3 database setup'
 
   subject { described_class.from(source).call(query) }
 
@@ -64,7 +64,7 @@
       data: [[20, 30],[1,2],%w[Homer Marge]]
   end
 
-  context 'raises error for invalid arguments' do # rubocop:disable RSpec/EmptyExampleGroup
+  context 'when raises error for invalid arguments' do # rubocop:disable RSpec/EmptyExampleGroup
     let(:query)  { Object.new                          }
     let(:source) { 'spec/fixtures/plaintext/bank2.dat' }
 
diff --git a/spec/support/shared_contexts.rb b/spec/support/shared_contexts.rb
index 02725c6..8e4f46f 100644
--- a/spec/support/shared_contexts.rb
+++ b/spec/support/shared_contexts.rb
@@ -1,4 +1,4 @@
-RSpec.shared_context 'sqlite3 database setup' do
+RSpec.shared_context 'with sqlite3 database setup' do
   module Daru
     module IO
       module Rspec
@@ -27,7 +27,7 @@ class Account < ActiveRecord::Base
   after { FileUtils.rm(db_name) }
 end
 
-RSpec.shared_context 'exporter setup' do
+RSpec.shared_context 'with exporter setup' do
   let(:tempfile) { Tempfile.new(filename) }
   let(:opts)     { {} }
   let(:df) do
diff --git a/spec/support/shared_examples.rb b/spec/support/shared_examples.rb
index 2aa4aac..dd4eb4d 100644
--- a/spec/support/shared_examples.rb
+++ b/spec/support/shared_examples.rb
@@ -22,7 +22,7 @@
 end
 
 RSpec.shared_examples 'importer with json-path option' do
-  context 'in temperature data' do
+  context 'when in temperature data' do
     let(:path) { 'spec/fixtures/json/temp.json' }
 
     context 'with only jsonpath columns' do
@@ -54,7 +54,7 @@
     end
   end
 
-  context 'in tv series data' do
+  context 'when in tv series data' do
     let(:path) { 'spec/fixtures/json/got.json' }
 
     context 'with jsonpath columns' do
@@ -101,7 +101,7 @@
     end
   end
 
-  context 'on allsets data' do
+  context 'when on allsets data' do
     let(:path) { 'spec/fixtures/json/allsets.json' }
 
     context 'with jsonpath columns' do
@@ -116,7 +116,7 @@
     end
   end
 
-  context 'on VAT data' do
+  context 'when on VAT data' do
     let(:path) { 'spec/fixtures/json/jsonvat.json' }
 
     context 'with jsonpath columns' do