SAS Software Development with the V-ModelAndrew RatcliffeRTSL.eu

Coders’ CornerPaper 124-2011

Overview

Best Practice in SAS software development Process… Flow from: requirements to deployment Via: design, build and test

Coding specifics A tip for testing your code

Andrew Ratcliffe First used SAS in 1983 Provide services through RTSL.eu Blogging on NOTECOLON.INFO

» SAS and software development best practice

Best Practice

Always driven and guided by business purpose

Repeatable set of steps Allows us to plan

» Time, cost, skills, effort Allows us to create templates and guidelines Helps newcomers contribute quickly and effectively Easier to transfer tasks between people

Plan – Do – Review Make sure everything got done… got done right

Barely adequate Good enough… but only just

Outline Development Process

What?

How?

Build

Test

DeployBusiness Case

Plan and Do

What?

How?

Build

Business Requirements

System Requirements

Design Specification

Unit Specification

Customer

Supplier

Traceability

What?

How?

Build

Business Requirements

System Requirements

Design Specification

Unit Specification

• Well-structured text, not prose

• Uniquely identify every element

• Make sure nothing is missed

• Make sure nothing is added

Testing

What?

How?

Build

Business Requirements

System Requirements

Design Specification

Unit Specification

User Acceptance

System

Integration

Unit

Peer Review

Test

Coding Standards

• Defined objectives

• Well-structured text, not prose

• Uniquely identify every element

• Repeatable steps

• Test Strategy defines approach, coverage, etc.

• Make sure nothing is missed/added

Test Strategy

Test Strategy

How will you be sure the system does what it should?

Types of testing Static / dynamic Inspection of results & data Baseline for comparison / expected results Automated / manual

Coverage 100% Spot checks

» How many / which & what

Artefacts & evidence to be archived

Test Strategy

Test Strategy - Detail

Units will leave environments as they found them Aside from planned / designed behaviour No memory leakage (memory freed-up at appropriate times) No temporary libraries remain assigned No temporary data sets remain No macro variables remain

141 %tharness(testmacro=BestCodeEver); THARNESS: Starting execution of code to be testedNLOBS=2.7481588701THARNESS: Execution of code to be tested has finished THARNESS: Summarising resultsTHARNESS: Macro variable has been added: scope=GLOBAL name=NLOBSTHARNESS: Library assignment has been added: libname=NFIND_METHARNESS: End of results summary

Coding Standards

Test Strategy

Deletes its own temporary WORK data sets Facilitated by the fact that the names of all of the macro’s WORK

data sets are prefixed with _THARNESS_ (achieved generically with _&sysmacroname._)

By using the same prefix, the data sets can be deleted at the end of the macro by specifying _THARNESS_: on PROC DATASETS’ DELETE statement

Conditional upon &tidy (for debugging)

%if %upcase(%substr(&tidy,1,1)) eq Y %then %do; proc datasets lib=work nolist; delete _&sysmacroname._: ; quit; options notes; %end; %mend tharness;

Approach: Snapshot then Compare Snapshot of elements of environment taken before and after

execution of the macro-under-test, e.g. sashelp.vslib

Comparison of before and after images done with DATA steps and PUT statements (more flexible than PROC COMPARE)

data _null_; merge work._&sysmacroname._vslibbefore (in=before) work._&sysmacroname._vslibafter (in=after) end=finish; by libname; retain IssueFound 0; if before and not after then do; put "&sysmacroname: Library assignment has been removed: " libname=; IssueFound=1; end; else if not before and after then do; put "&sysmacroname: Library assignment has been added: " libname=; IssueFound=1; end; if finish and not IssueFound then put "&sysmacroname: No library assignment issues found";run;

Approach: Snapshot then CompareData work._&sysmacroname._vslibBefore; Set sashelp.vslib;Run;

THARNESS: Library assignment has been added: libname=NFIND_ME

data _null_; merge work._&sysmacroname._vslibbefore (in=before) work._&sysmacroname._vslibafter (in=after) end=finish; by libname; retain IssueFound 0; if before and not after then do; put "&sysmacroname: Library assignment has been removed: " libname=; IssueFound=1; end; else if not before and after then do; put "&sysmacroname: Library assignment has been added: " libname=; IssueFound=1; end; if finish and not IssueFound then put "&sysmacroname: No library assignment issues found";run;

Echoes all of its parameters upon initiation Ensures that the values of those parameters taking default values

(and hence not specified in the calling program) are known to anybody inspecting the log

%macro tharness(testmacro = ,tidy = y ); %put &sysmacroname: Parameters received by this macro are:; %put _local_; %put ;

141 %tharness(testmacro=BestCodeEver);THARNESS: Parameters received by this macro are:THARNESS TESTMACRO BestCodeEverTHARNESS TIDY y

Summary

Plan – Do – Review

Barely Adequate

What – How - Build

Traceability (vertical)

Testing Traceability (horizontal) Peer review – unit – integration – system - user

Thank you for listening. Enjoy your evening!

Andrew Ratcliffe NOTECOLON.INFO