Year 10 · ICT · Spring 2

The systems life cycle; presentations · Lesson 2 of 5

Development, testing and implementation

Theory7.3 Development and testing7.4 Implementation

Year 10 · ICT · The systems life cycle; presentations · Lesson 2 of 5

You will learn to

  • Explain why a system must be tested before it is used.
  • Choose normal, abnormal and extreme test data and give the expected outcome.
  • Describe direct changeover, parallel running, pilot running and phased implementation.
  • Choose an implementation method for a scenario and justify it.

Year 10 · ICT · The systems life cycle; presentations · Lesson 2 of 5

Success criteria

You have got it when you can say:

  • I can complete a test plan row with test data and the expected outcome.
  • I can give normal, abnormal and extreme test data for a mark from 0 to 100.
  • I can explain why a hospital might choose parallel running.

Year 10 · ICT · The systems life cycle; presentations · Lesson 2 of 5

Retrieval starter

Questions from before. Write your answers, then show them.

  1. Last lesson

    Extreme test data is…

    A At the edges of the allowed rangeB Typical dataC Outside the range

    A. At the edges of the allowed range

  2. Last unit

    A line chart is for…

    A Unrelated categoriesB Change over timeC Parts of a whole

    B. Change over time

  3. Earlier this year

    A touch screen that senses the electricity in your finger is…

    A Infra-redB ResistiveC Capacitive

    C. Capacitive

Year 10 · ICT · The systems life cycle; presentations · Lesson 2 of 5

Key words (1 of 5)

Systems life cycle
The stages used to create a new system: analysis, design, development and testing, implementation, documentation, evaluation.
Systems analyst
The person who studies the current system and plans the new one.
System specification
A list of the hardware and software the new system needs.
Field
One item of data in a record, such as Surname.

Year 10 · ICT · The systems life cycle; presentations · Lesson 2 of 5

Key words (2 of 5)

Validation
An automatic computer check that data is sensible and allowed.
Check digit
An extra digit calculated from the other digits, used to detect input errors.
Data capture form
A paper or on-screen form used to collect data.
Test plan
A table listing each test, its data, the expected and actual outcomes and any remedial action.

Year 10 · ICT · The systems life cycle; presentations · Lesson 2 of 5

Key words (3 of 5)

Normal data
Sensible data that should be accepted.
Abnormal data
Data that should be rejected, such as out of range or the wrong type.
Extreme data
Data at the limits of the allowed range, which should be accepted.
Live data
Real data from the organisation, used to test the system with known results.

Year 10 · ICT · The systems life cycle; presentations · Lesson 2 of 5

Key words (4 of 5)

Remedial action
What was done to fix a test that failed.
Direct changeover
The old system stops and the new one starts immediately.
Parallel running
Old and new systems run together until the new one is trusted.
Pilot running
The new system is tried in one branch before the rest.

Year 10 · ICT · The systems life cycle; presentations · Lesson 2 of 5

Key words (5 of 5)

Phased implementation
The new system is introduced one part at a time across the organisation.

7.3 Development and testing · The explanation · step 1 of 7 · part 1 of 2

Why test, and the test strategy

Development means building the system: creating the file structures, forms, validation and reports.

Testing checks that the system works as the design says, and that it handles mistakes without crashing.

A test strategy decides what is tested and in what order: each module (a separate part), then each function (one task, such as 'record a loan'), then the whole system working together.

7.3 Development and testing · The explanation · step 1 of 7 · part 2 of 2

Why test, and the test strategy (continued)

e.g.Example
Library system modules: member records, book records, loans, reports. Test the loans module alone first. Then test the function 'return a book'. Then test the whole system: a new member borrows a book, returns it late, and appears on the overdue report.
?Why?

Testing small parts first makes errors easy to find. If the whole system fails at once, the fault could be anywhere.

7.3 Development and testing · The explanation · step 2 of 7 · part 1 of 3

Types of test data

Normal data is sensible data that the system should accept.

Abnormal data is data that should be rejected: outside the range or the wrong type. Some books call it erroneous data.

Extreme data is data at the very limits of what is allowed. It should be accepted.

Computer Science 0478 also uses boundary data: the limit value and the value immediately beyond it. ICT 0417 asks for normal, abnormal and extreme.

7.3 Development and testing · The explanation · step 2 of 7 · part 2 of 3

Types of test data (continued)

Field ruleNormalExtremeAbnormal
Exam mark 0 to 10056, 730, 100101, −5, 'sixty'
Year group 7 to 139, 117, 136, 14, 'ten'
Loan length 1 to 21 days141, 210, 22, 3.5

7.3 Development and testing · The explanation · step 2 of 7 · part 3 of 3

Types of test data (continued)

e.g.Example
Try the toy with the range 1 to 100. Classify 50, 1, 100, 0, 101 and 'abc'. Notice that 1 and 100 are extreme and accepted. 0 and 101 are rejected. ICT calls them abnormal. The toy labels them boundary, the Computer Science term for the value just outside the range.
!Watch out

Extreme data is accepted. Students often think extreme means 'too big'. Too big is abnormal.

There is something to try for this step in the IGCSE library.

7.3 Development and testing · The explanation · step 3 of 7 · part 1 of 3

The test plan

A test plan is a table written before testing. Each row is one test.

The first columns are: what is being tested, the test data and the type of data.

Then come the expected outcome (what should happen), the actual outcome (what did happen) and the remedial action (what was done to fix a failure).

If the actual outcome matches the expected outcome, the test passes. If not, the system is fixed and the test is run again.

7.3 Development and testing · The explanation · step 3 of 7 · part 2 of 3

The test plan (continued)

TestTest dataTypeExpected outcomeActual outcomeRemedial action
Mark field range 0 to 10056NormalAcceptedAcceptedNone needed
Mark field range 0 to 1000ExtremeAcceptedAcceptedNone needed
Mark field range 0 to 100100ExtremeAcceptedRejected with errorChanged rule from <100 to <=100, retested: accepted
Mark field range 0 to 100101AbnormalRejected, error message 'Mark must be 0 to 100'Rejected, message shownNone needed
Mark field range 0 to 100sixtyAbnormalRejected, error message 'Enter a number'Accepted and savedAdded type check, retested: rejected
Surname presence check(left blank)AbnormalRejected, 'Surname is required'Rejected, message shownNone needed

7.3 Development and testing · The explanation · step 3 of 7 · part 3 of 3

The test plan (continued)

?Why?

Writing the expected outcome before testing stops the tester accepting whatever happens. The test plan also becomes evidence in the technical documentation.

7.3 Development and testing · The explanation · step 4 of 7 · part 1 of 2

Live data

Live data is real data from the organisation, such as last month's actual library loans.

After testing with made-up test data, the system is tested with live data whose results are already known from the old system.

If the new system gives the same results as the old one, it is working correctly with real-world data.

7.3 Development and testing · The explanation · step 4 of 7 · part 2 of 2

Live data (continued)

e.g.Example
The library enters last October's 1,240 real loans. The old card system recorded 63 overdue books. The new system's overdue report should also show 63.
!Watch out

Live data contains real personal data, so it must be kept secure during testing.

7.4 Implementation · The explanation · step 6 of 7 · part 1 of 2

Advantages and disadvantages

Each method trades cost and speed against risk.

The key question: what happens if the new system fails?

MethodAdvantagesDisadvantages
DirectCheapest: only one system runs and staff do the work once. Benefits are immediate. Fastest.Highest risk: if the new system fails, there is no backup and work stops. Data could be lost. Staff must be fully trained before the switch.
ParallelLowest risk: if the new system fails, the old one is still working. Results can be compared to check the new system.Most expensive: staff do every job twice, so extra staff or overtime are needed. Takes longest. Data entered twice can lead to errors.
PilotIf it fails, only one branch is affected. Staff in the pilot branch can train others. Cheaper than parallel.Slow to reach the whole organisation. If the pilot branch fails, it suffers on its own. The pilot branch may not be typical of the others.
PhasedIf one part fails, only that part is affected and it can be fixed. Staff learn one part at a time.Slow: takes a long time to fully implement. Parts of old and new systems must work together, which is hard. Costly to evaluate each phase.

7.4 Implementation · The explanation · step 6 of 7 · part 2 of 2

Advantages and disadvantages (continued)

?Why?

There is no best method. The right one depends on how bad a failure would be, how much money there is, and whether the system can be split into branches or parts.

The explanation · 2 more steps

More on the lesson page

The lesson page has the rest of the explanation, step by step:

  • Four ways to change over
  • Choosing the right method

Open the lesson page

Year 10 · ICT · The systems life cycle; presentations · Lesson 2 of 5

Quick quiz · 1 of 3

A transition is…

  1. A An effect on one object
  2. B A note
  3. C The effect between slides

C. The effect between slides

Animation is the effect on an object within a slide.

Year 10 · ICT · The systems life cycle; presentations · Lesson 2 of 5

Quick quiz · 2 of 3

Presenter notes are seen by…

  1. A The speaker only
  2. B The audience
  3. C Nobody

A. The speaker only

Audience notes and handouts are for the audience.

Year 10 · ICT · The systems life cycle; presentations · Lesson 2 of 5

Quick quiz · 3 of 3

Handouts printed six to a page are for…

  1. A The projector
  2. B The audience to take away
  3. C The master slide

B. The audience to take away

The paper often asks for a specific number per page.

Year 10 · ICT · The systems life cycle; presentations · Lesson 2 of 5

Exit ticket

Answer on paper before you go. Then check.

  1. Validation checks that…

    A The data is what the person meantB The spelling is rightC The data is sensible: the right type and in range

    C. The data is sensible: the right type and in range It cannot know the truth, only the shape.

  2. Double data entry is…

    A VerificationB ValidationC Proof-reading

    A. Verification Typing it twice and comparing.