Essential Feed App – Image Feed Feature

BDD Specs

Story: Customer requests to see their image feed

Narrative #1

As an online customer I want the app to automatically load my latest image feed So I can always enjoy the newest images of my friends

Scenarios (Acceptance criteria)

Given the customer has connectivity
When the customer requests to see their feed
Then the app should display the latest feed from remote
  And replace the cache with the new feed

Narrative #2

As an offline customer I want the app to show the latest saved version of my image feed So I can always enjoy images of my friends

Scenarios (Acceptance criteria)

Given the customer doesn't have connectivity
And there’s a cached version of the feed
When the customer requests to see the feed
Then the app should display the latest feed saved

Given the customer doesn't have connectivity
And the cache is empty
When the customer requests to see the feed
Then the app should display an error message

Use Cases

Load Feed Use Case

Data:

• URL

Primary course (happy path):

1. Execute “Load Feed Items” command with above data.
2. System downloads data from the URL.
3. System validates downloaded data.
4. System creates feed items from valid data.
5. System delivers feed items.

Invalid data – error course (sad path):

1. System delivers error.

No connectivity – error course (sad path):

1. System delivers error.

Load Feed Fallback (Cache) Use Case

Data:

• Max age

Primary course:

1. Execute “Retrieve Feed Items” command with above data.
2. System fetches feed data from cache.
3. System validates cache age.
4. System creates feed items from cached data.
5. System delivers feed items.

Expired cache course (sad path):

1. System delivers no feed items.

Empty cache course (sad path):

1. System delivers no feed items.

Save Feed Items Use Case

Data:

• Feed items

Primary course (happy path):

1. Execute “Save Feed Items” command with above data.
2. System encodes feed items.
3. System timestamps the new cache.
4. System replaces the cache with new data.
5. System delivers success message.

Flowchart

Architecture

Model Specs

Feed Item

Payload contract

GET *url* (TBD)

200 RESPONSE

{
	"items": [
		{
			"id": "a UUID",
			"description": "a description",
			"location": "a location",
			"image": "https://a-image.url",
		},
		{
			"id": "another UUID",
			"description": "another description",
			"image": "https://another-image.url"
		},
		{
			"id": "even another UUID",
			"location": "even another location",
			"image": "https://even-another-image.url"
		},
		{
			"id": "yet another UUID",
			"image": "https://yet-another-image.url"
		}
		...
	]
}

GitHub

View Github