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Fake It While You
Make It
Kevin Murphy
The Gnar Company
@KEVIN_J_M
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Third-Party
Dependencies
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55
65
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55
65
MA
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Gnar Company Logo
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SWEATHR
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$11 Billion
SWEATHR @KEVIN_J_M
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$22 Billion?
SWEATHR @KEVIN_J_M
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SWEATHR
Third-party
dependency
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HTTP API
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class Location
end
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class Location
def sweater_weather?
end
end
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class Location
def sweater_weather?
uri = URI(conditions_url_for_zip_code)
end
end
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class Location
def sweater_weather?
uri = URI(conditions_url_for_zip_code)
result = Net::HTTP.get(uri)
end
end
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class Location
def sweater_weather?
uri = URI(conditions_url_for_zip_code)
result = Net::HTTP.get(uri)
response = JSON.parse(result)
end
end
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class Location
def sweater_weather?
uri = URI(conditions_url_for_zip_code)
result = Net::HTTP.get(uri)
response = JSON.parse(result)
feels_like = response.dig(
“current_observation”, “feelslike_f”)
end
end
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class Location
def sweater_weather?
uri = URI(conditions_url_for_zip_code)
result = Net::HTTP.get(uri)
response = JSON.parse(result)
feels_like = response.dig(
“current_observation”, “feelslike_f”)
feels_like.to_f.between?(55, 65)
end
end
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it "is time to break out the sweater" do
location = Sweathr::Location.new(
zip_code: “02108")
expect(location.sweater_weather?).to be true
end
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> rspec spec/sweathr/location_spec.rb
Failures:
1) Sweathr::Location#sweater_weather? is time to break out the
sweater
Failure/Error: expect(weather.sweater_weather?).to be true
expected true
got false
Finished in 0.36974 seconds (
fi
les took 0.2812 seconds to load)
1 example, 1 failure
70° F
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> rspec spec/sweathr/location_spec.rb
.
Finished in 0.37186 seconds (
fi
les took 0.48152 seconds to load)
1 example, 0 failures
63° F
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> rspec spec/sweathr/location_spec.rb
Failures:
1) Sweathr::Location#sweater_weather? is time to break out the
sweater
Failure/Error: expect(weather.sweater_weather?).to be true
expected true
got false
Finished in 0.36974 seconds (
fi
les took 0.2812 seconds to load)
1 example, 1 failure
53° F
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Direct Interaction
✓ Con
fi
dence
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Direct Interaction
✓ Con
fi
dence
✓ Production parity
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Direct Interaction
✓ Con
fi
dence
✓ Production parity
- Slow
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Direct Interaction
✓ Con
fi
dence
✓ Production parity
- Slow
- Non-deterministic
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Direct Interaction
✓ Con
fi
dence
✓ Production parity
- Slow
- Non-deterministic
- Dependency required
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Direct Interaction
✓ Con
fi
dence
✓ Production parity
- Slow
- Non-deterministic
- Dependency required
- Rate limiting
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Why Direct Interaction?
★ Unfamiliar with dependency
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Why Direct Interaction?
★ Unfamiliar with dependency
★ Low barrier to interact
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Stub
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before do
api_response = {
current_observation: {
feelslike_f: “55.0”
}
}.to_json
end
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before do
api_response = {
current_observation: {
feelslike_f: “55.0”
}
}.to_json
stub_request(:get, url)
.to_return(status: 200, body: api_response)
end
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it "is time to break out the sweater" do
location = Sweathr::Location.new(
zip_code: “02108")
expect(location.sweater_weather?).to be true
end
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Stub
✓ Deterministic
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Stub
✓ Deterministic
✓ Bypass dependency
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Stub
✓ Deterministic
✓ Bypass dependency
✓ Isolated unit
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Stub
✓ Deterministic
✓ Bypass dependency
✓ Isolated unit
- Must know response structure
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Stub
✓ Deterministic
✓ Bypass dependency
✓ Isolated unit
- Must know response structure
- Stub response vs. reality
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Stub
✓ Deterministic
✓ Bypass dependency
✓ Isolated unit
- Must know response structure
- Stub response vs. reality
- Possibly verbose
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Why Stub?
★ Stable interface
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Why Stub?
★ Stable interface
★ Small response
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Fake
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class FakeWeather < Sinatra::Base
end
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class FakeWeather < Sinatra::Base
get “/api/:key/conditions/q/:zip_code.json” do
end
end
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class FakeWeather < Sinatra::Base
get “/api/:key/conditions/q/:zip_code.json” do
json current_observation: { feelslike_f: "56.0" }
end
end
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it "is time to break out the sweater" do
location = Sweathr::Location.new(
zip_code: “02108”)
end
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it "is time to break out the sweater" do
location = Sweathr::Location.new(
zip_code: “02108”)
Capybara::Discoball.spin(FakeWeather) do |s|
end
end
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it "is time to break out the sweater" do
location = Sweathr::Location.new(
zip_code: “02108”)
Capybara::Discoball.spin(FakeWeather) do |s|
location.endpoint_url = s.url
end
end
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it "is time to break out the sweater" do
location = Sweathr::Location.new(
zip_code: “02108”)
Capybara::Discoball.spin(FakeWeather) do |s|
location.endpoint_url = s.url
expect(location.sweater_weather?).to be true
end
end
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Fake
✓ Full stack test
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Fake
✓ Full stack test
✓ Local, deployable sandbox
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Fake
✓ Full stack test
✓ Local, deployable sandbox
✓ Limited noise in setup
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Fake
✓ Full stack test
✓ Local, deployable sandbox
✓ Limited noise in setup
✓ Control fake complexity
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Fake
✓ Full stack test
✓ Local, deployable sandbox
✓ Limited noise in setup
✓ Control fake complexity
- Maintain consistency
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Fake
✓ Full stack test
✓ Local, deployable sandbox
✓ Limited noise in setup
✓ Control fake complexity
- Maintain consistency
- Test the fake
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Why Fake?
★ Need con
fi
dence in communication
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Why Fake?
★ Need con
fi
dence in communication
★ Multi-step interaction
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Fixture
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it "is time to break out the sweater" do
location = Sweathr::Location.new(
zip_code: “02108”)
end
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it "is time to break out the sweater" do
location = Sweathr::Location.new(
zip_code: “02108”)
VCR.use_cassette(“temp_needs_sweater") do
end
end
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it "is time to break out the sweater" do
location = Sweathr::Location.new(
zip_code: “02108”)
VCR.use_cassette(“temp_needs_sweater") do
expect(location.sweater_weather?).to be true
end
end
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Fixture
✓ Truth at moment in time
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Fixture
✓ Truth at moment in time
✓ Complete picture
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Fixture
✓ Truth at moment in time
✓ Complete picture
- Mystery guest
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Fixture
✓ Truth at moment in time
✓ Complete picture
- Mystery guest
- Snapshot in time
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Fixture
✓ Truth at moment in time
✓ Complete picture
- Mystery guest
- Snapshot in time
- Requires periodic system access
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Why Fixture?
★ Need complete response
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Why Fixture?
★ Need complete response
★ Dependency accessible
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Why Fixture?
★ Need complete response
★ Dependency accessible
★ Fixture creation limits impact on dependency
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Why Fixture?
★ Need complete response
★ Dependency accessible
★ Fixture creation limits impact on dependency
★ Can refresh regularly
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STOP
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class Location
def sweater_weather?
uri = URI(conditions_url_for_zip_code)
result = Net::HTTP.get(uri)
response = JSON.parse(result)
feels_like = response.dig(
“current_observation”, “feelslike_f”)
feels_like.to_f.between?(55, 65)
end
end
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class Location
def sweater_weather?
uri = URI(conditions_url_for_zip_code)
result = Net::HTTP.get(uri)
response = JSON.parse(result)
feels_like = response.dig(
“current_observation”, “feelslike_f”)
feels_like.to_f.between?(55, 65)
end
end
1
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class Location
def sweater_weather?
uri = URI(conditions_url_for_zip_code)
result = Net::HTTP.get(uri)
response = JSON.parse(result)
feels_like = response.dig(
“current_observation”, “feelslike_f”)
feels_like.to_f.between?(55, 65)
end
end
1
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class Location
def sweater_weather?
uri = URI(conditions_url_for_zip_code)
result = Net::HTTP.get(uri)
response = JSON.parse(result)
feels_like = response.dig(
“current_observation”, “feelslike_f”)
feels_like.to_f.between?(55, 65)
end
end
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3
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API Client
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module Sweathr
module Weather
class Api
end
end
end
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module Sweathr
module Weather
class Api
def current_conditions(zip:)
end
end
end
end
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module Sweathr
module Weather
class Api
def current_conditions(zip:)
uri = URI(
“#{auth_uri}/conditions/q/#{zip}.json”)
end
end
end
end
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module Sweathr
module Weather
class Api
def current_conditions(zip:)
uri = URI(
“#{auth_uri}/conditions/q/#{zip}.json”)
JSON.parse(Net::HTTP.get(uri))
end
end
end
end
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it "retrieves the current conditions" do
VCR.use_cassette("temp_needs_sweater") do
end
end
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it "retrieves the current conditions" do
VCR.use_cassette("temp_needs_sweater") do
result = api.current_conditions(zip: “02108")
end
end
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it "retrieves the current conditions" do
VCR.use_cassette("temp_needs_sweater") do
result = api.current_conditions(zip: “02108")
expect(result).to include(
"current_observation" => a_hash_including(
"feelslike_f" => a_kind_of(String)
)
)
end
end
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Data Representation
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module Sweathr
module Weather
class CurrentConditions
end
end
end
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module Sweathr
module Weather
class CurrentConditions
def initialize(results)
@results = results
end
end
end
end
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module Sweathr
module Weather
class CurrentConditions
def initialize(results)
@results = results
end
def feels_like_f
end
end
end
end
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module Sweathr
module Weather
class CurrentConditions
def initialize(results)
@results = results
end
def feels_like_f
value = @results.dig(
"current_observation", “feelslike_f")
end
end
end
end
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module Sweathr
module Weather
class CurrentConditions
def initialize(results)
@results = results
end
def feels_like_f
value = @results.dig(
"current_observation", “feelslike_f")
string_to_
fl
oat(value)
end
end
end
end
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describe "#feels_like_f" do
it “gives the feels like temp in Fahrenheit" do
end
end
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describe "#feels_like_f" do
it “gives the feels like temp in Fahrenheit" do
conditions =
Sweathr::Weather::CurrentConditions
.new(json)
end
end
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describe "#feels_like_f" do
it “gives the feels like temp in Fahrenheit" do
conditions =
Sweathr::Weather::CurrentConditions
.new(json)
expect(conditions.feels_like_f).to eq 55.5
end
end
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describe "#feels_like_f" do
it “gives the feels like temp in Fahrenheit" do
conditions =
Sweathr::Weather::CurrentConditions
.new(json)
expect(conditions.feels_like_f).to eq 55.5
end
context "with a non-numeric result";end
end
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describe "#feels_like_f" do
it “gives the feels like temp in Fahrenheit" do
conditions =
Sweathr::Weather::CurrentConditions
.new(json)
expect(conditions.feels_like_f).to eq 55.5
end
context "with a non-numeric result";end
context "with no current observation”;end
end
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describe "#feels_like_f" do
it "gives the feels like temp in Fahrenheit” do
conditions =
Sweathr::Weather::CurrentConditions
.new(json)
expect(conditions.feels_like_f).to eq 55.5
end
context "with a non-numeric result";end
context "with no current observation”;end
context "with no feels like f temperature";end
end
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Domain
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module Sweathr
module Weather
end
end
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module Sweathr
module Weather
def self.client
@client ||= Api.new
end
end
end
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module Sweathr
module Weather
def self.client
@client ||= Api.new
end
def self.current_conditions(zip_code:)
end
end
end
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module Sweathr
module Weather
def self.client
@client ||= Api.new
end
def self.current_conditions(zip_code:)
Sweathr::Weather::CurrentConditions.new(
client.current_conditions(zip: zip_code))
end
end
end
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Implementation
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class Location
def sweater_weather?
end
end
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class Location
def sweater_weather?
current =
Sweathr::Weather.current_conditions(
zip_code: @zip_code)
end
end
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class Location
def sweater_weather?
current =
Sweathr::Weather.current_conditions(
zip_code: @zip_code)
current.feels_like_f.between?(55, 65)
end
end
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module Sweathr
module Weather
def self.client
@client ||= Api.new
end
end
end
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module Sweathr
module Weather
def self.client
@client ||= Api.new
end
def self.client=(client)
end
end
end
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module Sweathr
module Weather
def self.client
@client ||= Api.new
end
def self.client=(client)
@client = client
end
end
end
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Fake Client
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class FakeWeatherClient
end
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class FakeWeatherClient
def current_conditions(zip:)
end
end
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class FakeWeatherClient
def current_conditions(zip:)
{
"current_observation" => {
"feelslike_f" => @results[zip_code]
}
}
end
end
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class FakeWeatherClient
def current_conditions(zip:)
{
"current_observation" => {
"feelslike_f" => @results[zip_code]
}
}
end
def add_condition(zip_code:, temp_f:)
end
end
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class FakeWeatherClient
def current_conditions(zip:)
{
"current_observation" => {
"feelslike_f" => @results[zip_code]
}
}
end
def add_condition(zip_code:, temp_f:)
@results[zip_code] = temp_f
end
end
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Test Mode
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module Sweathr
module Testing
end
end
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module Sweathr
module Testing
def self.enable!
end
end
end
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module Sweathr
module Testing
def self.enable!
Sweathr::Weather.client =
FakeWeatherClient.new
end
end
end
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module Sweathr
module Testing
def self.enable!
Sweathr::Weather.client =
FakeWeatherClient.new
end
def self.disable!
end
end
end
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module Sweathr
module Testing
def self.enable!
Sweathr::Weather.client =
FakeWeatherClient.new
end
def self.disable!
Sweathr::Weather.client =
Sweathr::Weather::Api.new
end
end
end
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Testing
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it "is time to break out the sweater" do
end
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it "is time to break out the sweater" do
Sweathr::Testing.enable!
end
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it "is time to break out the sweater" do
Sweathr::Testing.enable!
Sweathr::Weather.client.add_condition(
zip_code: "02108", temp_f: “56.0")
end
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it "is time to break out the sweater" do
Sweathr::Testing.enable!
Sweathr::Weather.client.add_condition(
zip_code: "02108", temp_f: “56.0")
location = Sweathr::Location.new(
zip_code: “02108”)
end
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it "is time to break out the sweater" do
Sweathr::Testing.enable!
Sweathr::Weather.client.add_condition(
zip_code: "02108", temp_f: “56.0")
location = Sweathr::Location.new(
zip_code: “02108”)
expect(location.sweater_weather?).to be true
end
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it "is time to break out the sweater" do
Sweathr::Testing.enable!
Sweathr::Weather.client.add_condition(
zip_code: "02108", temp_f: “56.0")
location = Sweathr::Location.new(
zip_code: “02108”)
expect(location.sweater_weather?).to be true
Sweathr::Testing.disable!
end
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Test Mode
✓ Speed
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Test Mode
✓ Speed
✓ State control
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Test Mode
✓ Speed
✓ State control
✓ Metadata tracking
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Test Mode
✓ Speed
✓ State control
✓ Metadata tracking
- No dependency interaction
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Test Mode
✓ Speed
✓ State control
✓ Metadata tracking
- No dependency interaction
- Test mode vs. reality
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Why Test Mode?
★ Have dependency coverage elsewhere
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Why Test Mode?
★ Have dependency coverage elsewhere
★ Need interaction with results
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Testing Third-Party
Dependencies?
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DON’T*
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Client
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Client Data
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Client Data Domain
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Client Data Domain
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Client Data Domain
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Client Data Domain
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Client Data Domain
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Limit Interaction
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Limit Interaction
Test Con
fi
dently
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Gnar Company Logo
https://github.com/kevin-j-m/testing-services
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https://thegnar.co