SAFE-COMMIT Analysis to Facilitate
Team Software Development
Jan Wloka
PROLANGS
Rutgers University
Barbara G. Ryder Frank Tip Xiaoxia Ren
Virginia Tech IBM Research Rutgers University
© Jan Wloka 2009 All Rights reserved.

Parallel Work on Shared Code
Problems: Merge conflicts, duplicative work
Revision control systems (RCS) detect
\"direct\" merge conflicts
Commit policy governs commit process
“Commit early and commit often.”
“Don’t commit compilation or test failures.”
© Jan Wloka 2009 All Rights reserved. 2

Parallel Work on Shared Code
Problems: Merge conflicts, duplicative work
Revision control systems (RCS) detect
\"direct\" merge conflicts
Commit policy governs commit process
“Commit early and commit often.”
“Don’t commit compilation or test failures.”
Problems are still not solved!
RCS offer limited conflict detection/resolution
Policies are not enforced
Policies may be too restrictive
© Jan Wloka 2009 All Rights reserved. 2

Enforceable SAFE-COMMIT Policies
Idea: Observe effects on test results to detect unsafe
changes, e.g.:
Changes affect a failing test
Changes affect a worsening test
Changes not tested
© Jan Wloka 2009 All Rights reserved. 3

Enforceable SAFE-COMMIT Policies
Idea: Observe effects on test results to detect unsafe
changes, e.g.:
Changes affect a failing test
Changes affect a worsening test
Changes not tested
Policies of varying degrees of strictness (intuition)
Commit changes that affect only passing tests
Commit changes that affect only non-worsening tests
Commit changes that don’t degrade test outcomes
© Jan Wloka 2009 All Rights reserved. 3

Change Models
[PASTE’01, OOPSLA’04, ICSE’05, TSE’06, ICSE’09]
Decompose an edit into 19 distinct atomic changes
Reflecting language semantics
Are atomic
Potential change in dispatch behavior
Lookup change: explicit effect on a dispatch entry
Inter-dependences between changes
Syntactic, structural requirements
Cause – effect mapping
© Jan Wloka 2009 All Rights reserved. 4

Explicit Representation of Change
class A { public class Tests extends TestCase { Test
int y; public void test1() {
int zip(int x) { A a = new A();
this.y = x; a.bar(3); test
x = zap(x); assertEquals(5, a.zip(3));
test
return x + 2; }
public void test2() { test
}
A a = new A();
int zap(int x) { return 2 * x; } test
int temp = a.bar(2);
int foo(int x) { return 2 * x; }
assertEquals(2, a.foo(temp)); test
int bar(int x) { return x / 2 ; } }
int wiff(int x) { return x; } public void test3() {
int baz(int x) { return x + 1; } B b = new B();
int val() { return 2; } assertEquals(5, b.waff(5));
} }
class B extends A { public void test4() {
int waff(int x) { this.y = x; return x; } B b = new B();
int bla(int x) { return 7 + this.val(); } assertEquals(8, b.bla(5));
int val() { return 1; } }
public void test5() {
}
A a = new B();
assertEquals(a.baz(1), a.val());
}
© Jan Wloka 2009 All Rights reserved. } 5

Explicit Representation of Change
Class
class A { A public class Tests extends TestCase { Test
Method void test1() Method
public Method { Method
int y;
foo(int) = new A();
A a bar(int) wiff(int) baz(int)
int zip(int x) {
this.y = x; a.bar(3); test
x = zap(x); assertEquals(5, a.zip(3));
test
return x + 2; }
public void test2() { test
}
A a = new A();
int zap(int x) { return 2 * x; } test
Field tempMethod
int = a.bar(2);
Method Method
int foo(int x) { return 2 * x; }
assertEquals(2, a.foo(temp)); val()
y zip(int) zap() test
int bar(int x) { return x / 2 ; } }
int wiff(int x) { return x; } public void test3() {
int baz(int x) { return x + 1; } Class B b = new B();
int val() { return 2; } B
assertEquals(5, b.waff(5));
} }
class B extends A { Method void test4() Method
public Method {
int waff(int x) { this.y = x; return x; } waff(int) = new B();
B b bla(int) val()
int bla(int x) { return 7 + this.val(); } assertEquals(8, b.bla(5));
int val() { return 1; } }
public void test5() {
}
A a = new B();
assertEquals(a.baz(1), a.val());
}
© Jan Wloka 2009 All Rights reserved. } 5

Explicit Representation of Change
Class
class A { A public class Tests extends TestCase { Test
Method void test1() Method
public Method { Method
int y;
foo(int) = new A();
A a bar(int) wiff(int) baz(int)
int zip(int x) {
this.y = x; a.bar(3); AM test
x = zap(x); assertEquals(5, a.zip(3));
test
return x + 2; }
public void test2() { test
}
A a = new A();
int zap(int x) { return 2 * x; } test
Field tempMethod
int = a.bar(2);
Method Method
int foo(int x) { return 2 * x; }
assertEquals(2, a.foo(temp)); val()
y zip(int) zap() test
int bar(int x) { return x / 2 ; } }
AF AM
int wiff(int x) { return x; } public void test3() {
int baz(int x) { return x + 1; } Class B b = new B();
int val() { return 2; } B
assertEquals(5, b.waff(5));
} }
class B extends A { Method void test4() Method
public Method {
int waff(int x) { this.y = x; return x; } waff(int) = new B();
B b bla(int) val()
int bla(int x) { return 7 + this.val(); } assertEquals(8, b.bla(5));
DM
int val() { return 1; } }
public void test5() {
}
A a = new B();
assertEquals(a.baz(1), a.val());
}
© Jan Wloka 2009 All Rights reserved. } 5

Explicit Representation of Change
Class
class A { A public class Tests extends TestCase { Test
Method void test1() Method
public Method { Method
int y;
foo(int) = new A();
A a bar(int) wiff(int) baz(int)
int zip(int x) {
CM a.bar(3); CM AM CM test
this.y = x;
CM
assertEquals(5, a.zip(3));
x = zap(x); test
return x + 2; }
public void test2() { test
}
A a = new A();
int zap(int x) { return 2 * x; } test
Field tempMethod
int = a.bar(2);
Method Method
int foo(int x) { return 2 * x; }
assertEquals(2, a.foo(temp)); val()
y zip(int) zap() test
int bar(int x) { return x / 2 ; } }
AF CM AM
int wiff(int x) { return x; } public void test3() CM {
int baz(int x) { return x + 1; } Class B b = new B();
int val() { return 2; } B
assertEquals(5, b.waff(5));
} }
class B extends A { Method void test4() Method
public Method {
int waff(int x) { this.y = x; return x; } waff(int) = new B();
B b bla(int) val()
int bla(int x) { return 7 + this.val(); } CM assertEquals(8, b.bla(5));
CM DM
int val() { return 1; } }
CM
public void test5() {
}
A a = new B();
assertEquals(a.baz(1), a.val());
}
© Jan Wloka 2009 All Rights reserved. } 5

Explicit Representation of Change
Class
class A { A public class Tests extends TestCase { Test
Method void test1() Method
public Method { Method
int y;
foo(int) = new A();
A a bar(int) wiff(int) baz(int)
int zip(int x) {
CM a.bar(3); CM AM CM test
this.y = x;
CM
assertEquals(5, a.zip(3));
x = zap(x); test
return x + 2; }
public void test2() { test
}
A a = new A();
int zap(int x) { return 2 * x; } test
Field tempMethod
int = a.bar(2);
Method Method
int foo(int x) { return 2 * x; }
assertEquals(2, a.foo(temp)); val()
y zip(int) zap() test
int bar(int x) { return x / 2 ; } }
AF CM AM
int wiff(int x) { return x; } public void test3() CM {
int baz(int x) { return x + 1; } Class B b = new B();
int val() { return 2; } B
assertEquals(5, b.waff(5));
} }
class B extends A { Method void test4() Method
public Method {
int waff(int x) { this.y = x; return x; } waff(int) = new B();
B b bla(int) val()
int bla(int x) { return 7 + this.val(); } CM assertEquals(8, b.bla(5));
CM DM
int val() { return 1; } }
CM
public void test5() {
}
A a = new B();
assertEquals(a.baz(1), a.val());
}
© Jan Wloka 2009 All Rights reserved. } 5

Explicit Representation of Change
Class
class A { A public class Tests extends TestCase { Test
Method void test1() Method
public Method { Method
int y;
foo(int) = new A();
A a bar(int) wiff(int) baz(int)
int zip(int x) {
CM a.bar(3); CM AM CM test
this.y = x;
CM
assertEquals(5, a.zip(3));
x = zap(x); test
} LC
return x + 2;
public void test2() { LC test
}
A a = new A();
int zap(int x) { return 2 * x; } test
Field tempMethod
int = a.bar(2);
Method Method
int foo(int x) { return 2 * x; }
assertEquals(2, a.foo(temp)); val()
y zip(int) zap() test
int bar(int x) { return x / 2 ; } }
AF CM AM LC
int wiff(int x) { return x; } public void test3() CM {
int baz(int x) { return x + 1; } Class B b = new B();
B LC
int val() { return 2; } assertEquals(5, b.waff(5));
LC
} }
class B extends A { Method void test4() Method
public Method {
int waff(int x) { this.y = x; return x; } waff(int) = new B();
B b bla(int) val()
int bla(int x) { return 7 + this.val(); } CM assertEquals(8, b.bla(5));
CM DM
int val() { return 1; } }
CM
public void test5() {
} LC
A a = new B();
assertEquals(a.baz(1), a.val());
}
© Jan Wloka 2009 All Rights reserved. } 5

Determining Effects on Program
Behavior
Program Source Code Atomic Change Model Program Behavior
AST :: original
P
I C
M M
AST :: edited
P
I C C
M M M M
© Jan Wloka 2009 All Rights reserved. 6

Determining Effects on Program
Behavior
Program Source Code Atomic Change Model Program Behavior
AST :: original
P
I C
C
M M
M M
AST :: edited
P
I C C
M M M M
© Jan Wloka 2009 All Rights reserved. 6

Determining Effects on Program
Behavior
Program Source Code Atomic Change Model Program Behavior
AST :: original
P
I C
AC
C
M M
AM AM
M M
AST :: edited
P CM CM
I C C
M M M M
© Jan Wloka 2009 All Rights reserved. 6

Determining Effects on Program
Behavior
Program Source Code Atomic Change Model Program Behavior
AST :: original LC
P
LC
I C
AC
C
M M
LC
AM AM
M M
AST :: edited
P CM CM
I C C
M M M M
© Jan Wloka 2009 All Rights reserved. 6

Determining Effects on Program
Behavior
Program Source Code Atomic Change Model Program Behavior
AST :: original LC
call graph :: test1
P
LC
I C
AC
C
M M
LC
AM AM call graph :: test2
M M
AST :: edited
P CM CM
I C C
M M M M
© Jan Wloka 2009 All Rights reserved. 6

Determining Effects on Program
Behavior
Program Source Code Atomic Change Model Program Behavior
AST :: original LC
call graph :: test1
P
LC
I C
AC
C
M M
LC
AM AM call graph :: test2
M M
AST :: edited
P CM CM
I C C
M M M M
© Jan Wloka 2009 All Rights reserved. 6

Determining Effects on Program
Behavior
Program Source Code Atomic Change Model Program Behavior
AST :: original LC
call graph :: test1
P
LC
I C
AC
C
M M
LC
AM AM call graph :: test2
M M
AST :: edited
P CM CM
I C C
M M M M
© Jan Wloka 2009 All Rights reserved. 6

Determining Effects on Program
Behavior
Program Source Code Atomic Change Model Program Behavior
AST :: original LC
call graph :: test1
P
LC
I C
AC
C
M M
LC
AM AM call graph :: test2
M M
AST :: edited
P CM CM
I C C
M M M M
© Jan Wloka 2009 All Rights reserved. 6

Determining Effects on Program
Behavior
Program Source Code Atomic Change Model Program Behavior
AST :: original LC
call graph :: test1
P
LC
I C
AC
C
M M
LC
AM AM call graph :: test2
M M
AST :: edited
P CM CM
I C C
M M M M
© Jan Wloka 2009 All Rights reserved. 6

Determining Effects on Program
Behavior
Program Source Code Atomic Change Model Program Behavior
AST :: original LC
call graph :: test1
P
LC
I C
AC
C
M M
LC
AM AM call graph :: test2
M M
AST :: edited
P CM CM
I C C
M M M M
© Jan Wloka 2009 All Rights reserved. 6

Classifications of Unsafe Changes
Definition Change Coverage: A change c is covered by a
test t if
(i) c is exercised by t
(ii) c depends on c′, c′ is covered by t, or
(iii) c′ depends on c , c′ is covered by t.
© Jan Wloka 2009 All Rights reserved. 7

Classifications of Unsafe Changes
Definition Change Coverage: A change c is covered by a
test t if
(i) c is exercised by t
(ii) c depends on c′, c′ is covered by t, or Test Outcomes
pass → pass
(iii) c′ depends on c , c′ is covered by t. fail → pass
Classification of test outcomes pass → fail
fail → fail
Passing: {p→p, f→p, ∅→p} ∅ → pass
Not worsening: Passing + {f→f, ∅→f} ∅ → fail
pass → ∅
Worsening: {p→f}
fail → ∅
© Jan Wloka 2009 All Rights reserved. 7

Classifications of Unsafe Changes
Definition Change Coverage: A change c is covered by a
test t if
(i) c is exercised by t
(ii) c depends on c′, c′ is covered by t, or Test Outcomes
pass → pass
(iii) c′ depends on c , c′ is covered by t. fail → pass
Classification of test outcomes pass → fail
fail → fail
Passing: {p→p, f→p, ∅→p} ∅ → pass
Not worsening: Passing + {f→f, ∅→f} ∅ → fail
pass → ∅
Worsening: {p→f}
fail → ∅
➾ E.g, c is unsafe, because it’s covered by a worsening test.
© Jan Wloka 2009 All Rights reserved. 7

Preserving Test Behavior
public class Tests extends TestCase {
public void test1() {
A a = new A();
a.bar(3);
assertEquals(5, a.zip(3));
}
public void test2() { /* ... */ }
public void test3() { /* ... */ }
public void test4() { /* ... */ }
public void test5() { /* ... */ }
}
{ Test Results
original edited
test1 ! \"
test2 ! !
test3 ! !
test4 ! \"
test5 ! !
© Jan Wloka 2009 All Rights reserved. 8

Preserving Test Behavior
public class Tests extends TestCase {
public void test1() {
A a = new A();
a.bar(3);
assertEquals(5, a.zip(3)); Tests.test1()
}
<A,A.bar()> <A,A.zip()>
public void test2() { /* ... */ }
public void test3() { /* ... */ }
A.A() A.bar() A.zip() Assert.assertEquals()
public void test4() { /* ... */ }
public void test5() { /* ... */ }
} <A,A.zap()>
{ Test Results A.zap()
original edited
test1 ! \"
test2 ! !
test3 ! !
test4 ! \"
test5 ! !
© Jan Wloka 2009 All Rights reserved. 8

Preserving Test Behavior
public class Tests extends TestCase {
public void test1() {
A a = new A();
a.bar(3);
assertEquals(5, a.zip(3)); Tests.test1()
}
<A,A.bar()> <A,A.zip()>
public void test2() { /* ... */ }
public void test3() { /* ... */ }
A.A() A.bar() A.zip() Assert.assertEquals()
public void test4() { /* ... */ }
public void test5() { /* ... */ } CM1 CM2
} <A,A.zap()>
{ Test Results A.zap()
CM:B.waff() AF:A.y
original edited CM3
LC1
test1 ! \"
LC2:<B,A.zap()> AM1:A.zap()
test2 ! !
test3 ! !
test4 ! \"
test5 ! !
© Jan Wloka 2009 All Rights reserved. 8

Preserving Test Behavior
public class Tests extends TestCase {
public void test1() {
A a = new A();
a.bar(3);
assertEquals(5, a.zip(3)); Tests.test1()
}
<A,A.bar()> <A,A.zip()>
public void test2() { /* ... */ }
public void test3() { /* ... */ }
A.A() A.bar() A.zip() Assert.assertEquals()
public void test4() { /* ... */ }
public void test5() { /* ... */ } CM1 CM2
} <A,A.zap()>
{ Test Results A.zap()
CM:B.waff() AF:A.y
original edited CM3
LC1
test1 ! \"
LC2:<B,A.zap()> AM1:A.zap()
test2 ! !
test3 ! !
test4 ! \"
test5 ! !
© Jan Wloka 2009 All Rights reserved. 8

Preserving Test Behavior
public class Tests extends TestCase {
public void test1() {
A a = new A();
a.bar(3);
assertEquals(5, a.zip(3)); Tests.test1()
}
<A,A.bar()> <A,A.zip()>
public void test2() { /* ... */ }
public void test3() { /* ... */ }
A.A() A.bar() A.zip() Assert.assertEquals()
public void test4() { /* ... */ }
public void test5() { /* ... */ } CM1 CM2
} <A,A.zap()>
{ Test Results A.zap()
CM:B.waff() AF:A.y
original edited CM3
LC1
test1 ! \"
LC2:<B,A.zap()> AM1:A.zap()
test2 ! !
test3 ! !
test4 ! \"
test5 ! !
© Jan Wloka 2009 All Rights reserved. 8

Preserving Test Behavior
public class Tests extends TestCase {
public void test1() {
A a = new A();
a.bar(3);
assertEquals(5, a.zip(3)); Tests.test1()
}
<A,A.bar()> <A,A.zip()>
public void test2() { /* ... */ }
public void test3() { /* ... */ }
A.A() A.bar() A.zip() Assert.assertEquals()
public void test4() { /* ... */ }
public void test5() { /* ... */ } CM1 CM2
} <A,A.zap()>
{ Test Results A.zap()
CM:B.waff() AF:A.y
original edited CM3
LC1
test1 ! \"
LC2:<B,A.zap()> AM1:A.zap()
test2 ! !
test3 ! !
test4 ! \"
{CM1, CM2, CM3, LC1, LC2, AM1}
test5 ! ! may affect a worsening test.
© Jan Wloka 2009 All Rights reserved. 8

SAFE-COMMIT Algorithm Sk etch
Input: CHANGES, EXERCISED(t), COVERED(t), INPUTTESTS
Add INPUTTESTS to set PRESERVEDTESTS
Step1: Selection of NONCOMMITTABLE
Find changes in EXERCISED(t)
Find changes in DEPENDENCES(c)
Step2: Selection of new PRESERVEDTESTS
Find tests t : COVERED(t) contains c in NONCOMMITTABLE
COMMITTABLE= CHANGES \\ (NONCOMMITTABLE ∪ UNCOVERED)
Output: COMMITTABLE, PRESERVEDTESTS
© Jan Wloka 2009 All Rights reserved. 9

SAFE-COMMIT Example Run
Example: Find all successfully tested changes.
AM:A.zap() LC:<A, A.zap()> CM:A.bar() CM:A.foo()
CM:A.zap test1() test2() test3()
LC:<B, A.zap()> CM:A.zip() AF:A.y CM:B.waff()
DM:B.val() LC:<B, A.val()>
CM:A.wiff()
AM:B.wiff() LC:<A, A.wiff()> CM:B.bla() LC:<[B, B.val()> CM:B.val()
CM:A.baz()
LC:<B, A.wiff()>
test4() test5()
© Jan Wloka 2009 All Rights reserved. 10

SAFE-COMMIT Example Run
Example: Find all successfully tested changes.
AM:A.zap() LC:<A, A.zap()> CM:A.bar() CM:A.foo()
CM:A.zap test1() test2() test3()
LC:<B, A.zap()> CM:A.zip() AF:A.y CM:B.waff()
DM:B.val() LC:<B, A.val()>
CM:A.wiff()
AM:B.wiff() LC:<A, A.wiff()> CM:B.bla() LC:<[B, B.val()> CM:B.val()
CM:A.baz()
LC:<B, A.wiff()>
test4() test5()
© Jan Wloka 2009 All Rights reserved. 10

SAFE-COMMIT Example Run
Example: Find all successfully tested changes.
AM:A.zap() LC:<A, A.zap()> CM:A.bar() CM:A.foo()
CM:A.zap test1() test2() test3()
LC:<B, A.zap()> CM:A.zip() AF:A.y CM:B.waff()
DM:B.val() LC:<B, A.val()>
CM:A.wiff()
AM:B.wiff() LC:<A, A.wiff()> CM:B.bla() LC:<[B, B.val()> CM:B.val()
CM:A.baz()
LC:<B, A.wiff()>
test4() test5()
© Jan Wloka 2009 All Rights reserved. 10

SAFE-COMMIT Example Run
Example: Find all successfully tested changes.
AM:A.zap() LC:<A, A.zap()> CM:A.bar() CM:A.foo()
CM:A.zap test1() test2() test3()
LC:<B, A.zap()> CM:A.zip() AF:A.y CM:B.waff()
DM:B.val() LC:<B, A.val()>
CM:A.wiff()
AM:B.wiff() LC:<A, A.wiff()> CM:B.bla() LC:<[B, B.val()> CM:B.val()
CM:A.baz()
LC:<B, A.wiff()>
test4() test5()
© Jan Wloka 2009 All Rights reserved. 10

SAFE-COMMIT Example Run
Example: Find all successfully tested changes.
AM:A.zap() LC:<A, A.zap()> CM:A.bar() CM:A.foo()
CM:A.zap test1() test2() test3()
LC:<B, A.zap()> CM:A.zip() AF:A.y CM:B.waff()
DM:B.val() LC:<B, A.val()>
CM:A.wiff()
AM:B.wiff() LC:<A, A.wiff()> CM:B.bla() LC:<[B, B.val()> CM:B.val()
CM:A.baz()
LC:<B, A.wiff()>
test4() test5()
© Jan Wloka 2009 All Rights reserved. 10

SAFE-COMMIT Example Run
Example: Find all successfully tested changes.
AM:A.zap() LC:<A, A.zap()> CM:A.bar() CM:A.foo()
CM:A.zap test1() test2() test3()
LC:<B, A.zap()> CM:A.zip() AF:A.y CM:B.waff()
DM:B.val() LC:<B, A.val()>
CM:A.wiff()
AM:B.wiff() LC:<A, A.wiff()> CM:B.bla() LC:<[B, B.val()> CM:B.val()
CM:A.baz()
LC:<B, A.wiff()>
test4() test5()
© Jan Wloka 2009 All Rights reserved. 10

SAFE-COMMIT Example Run
Example: Find all successfully tested changes.
AM:A.zap() LC:<A, A.zap()> CM:A.bar() CM:A.foo()
CM:A.zap test1() test2() test3()
LC:<B, A.zap()> CM:A.zip() AF:A.y CM:B.waff()
DM:B.val() LC:<B, A.val()>
CM:A.wiff()
AM:B.wiff() LC:<A, A.wiff()> CM:B.bla() LC:<[B, B.val()> CM:B.val()
CM:A.baz()
LC:<B, A.wiff()>
test4() test5()
© Jan Wloka 2009 All Rights reserved. 10

SAFE-COMMIT Example Run
Example: Find all successfully tested changes.
AM:A.zap() LC:<A, A.zap()> CM:A.bar() CM:A.foo()
CM:A.zap test1() test2() test3()
LC:<B, A.zap()> CM:A.zip() AF:A.y CM:B.waff()
DM:B.val() LC:<B, A.val()>
CM:A.wiff()
AM:B.wiff() LC:<A, A.wiff()> CM:B.bla() LC:<[B, B.val()> CM:B.val()
CM:A.baz()
LC:<B, A.wiff()>
test4() test5()
© Jan Wloka 2009 All Rights reserved. 10

SAFE-COMMIT Example Run
Example: Find all successfully tested changes.
AM:A.zap() LC:<A, A.zap()> CM:A.bar() CM:A.foo()
CM:A.zap test1() test2() test3()
LC:<B, A.zap()> CM:A.zip() AF:A.y CM:B.waff()
DM:B.val() LC:<B, A.val()>
CM:A.wiff()
AM:B.wiff() LC:<A, A.wiff()> CM:B.bla() LC:<[B, B.val()> CM:B.val()
CM:A.baz()
LC:<B, A.wiff()>
test4() test5()
© Jan Wloka 2009 All Rights reserved. 10

SAFE-COMMIT Example Run
Example: Find all successfully tested changes.
AM:A.zap() LC:<A, A.zap()> CM:A.bar() CM:A.foo()
CM:A.zap test1() test2() test3()
LC:<B, A.zap()> CM:A.zip() AF:A.y CM:B.waff()
DM:B.val() LC:<B, A.val()>
CM:A.wiff()
AM:B.wiff() LC:<A, A.wiff()> CM:B.bla() LC:<[B, B.val()> CM:B.val()
CM:A.baz()
LC:<B, A.wiff()>
test4() test5()
© Jan Wloka 2009 All Rights reserved. 10

SAFE-COMMIT Example Run
Example: Find all successfully tested changes.
AM:A.zap() LC:<A, A.zap()> CM:A.bar() CM:A.foo()
CM:A.zap test1() test2() test3()
LC:<B, A.zap()> CM:A.zip() AF:A.y CM:B.waff()
DM:B.val() LC:<B, A.val()>
CM:A.wiff()
AM:B.wiff() LC:<A, A.wiff()> CM:B.bla() LC:<[B, B.val()> CM:B.val()
CM:A.baz()
LC:<B, A.wiff()>
test4() test5()
© Jan Wloka 2009 All Rights reserved. 10

SAFE-COMMIT Example Run
Example: Find all successfully tested changes.
AM:A.zap() LC:<A, A.zap()> CM:A.bar() CM:A.foo()
CM:A.zap test1() test2() test3()
LC:<B, A.zap()> CM:A.zip() AF:A.y CM:B.waff()
DM:B.val() LC:<B, A.val()>
CM:A.wiff()
AM:B.wiff() LC:<A, A.wiff()> CM:B.bla() LC:<[B, B.val()> CM:B.val()
CM:A.baz()
LC:<B, A.wiff()>
test4() test5()
© Jan Wloka 2009 All Rights reserved. 10

Modeling Commit Policies
RESTRICTIVE: “Covered by passing tests only”
Tight control of commits
E.g., major release is imminent
MODERATE: “Covered by non-worsening tests only”
Tested changes, that don't degrade test outcomes
E.g., for test-first methodologies
PERMISSIVE: “Not covered by a worsening test”
Moderate Policy + untested changes
E.g., for technology prototypes
© Jan Wloka 2009 All Rights reserved. 11

Experiments
Goal: Set of committable changes is significant!
Bi-weekly repository snapshots of Daikon
Six pairs with failling tests
Daikon
Version Avg p1 p2 p3 p4 p5 p6
Changes 1751 274 1485 614 302 6050
Covered 1013 5 1225 20 130 185
Restrictive Total % 4.6 6.3 1.5 1.8 1.0 16.6 0.5
Moderate Total % 31.4 57.9 1.5 82.5 3.3 43.0 0.5
Permissive Total % 99.5 100 99.6 100 100 100 97.4
© Jan Wloka 2009 All Rights reserved. 12

Experiments
Goal: Set of committable changes is significant!
Bi-weekly repository snapshots of Daikon
Six pairs with failling tests
Daikon
Version Avg p1 p2 p3 p4 p5 p6
Changes 1751 274 1485 614 302 6050
Covered 1013 5 1225 20 130 185
Total % 4.6 6.3 1.5 1.8 1.0 16.6 0.5
Restrictive
Covered % 29.4 11.0 80.0 2.1 30.0 38.5 15.1
Total % 31.4 57.9 1.5 82.5 3.3 43.0 0.5
Moderate
Covered % 82.5 100 80.0 100 100 100 15.1
Permissive Total % 99.5 100 99.6 100 100 100 97.4
© Jan Wloka 2009 All Rights reserved. 12

Related Work
Revision Control, Software Merging
No indirect merge conflicts, manual resolution
SAFE-COMMIT semantic detection w/ behavior in tests
Workspace Awareness Tools
Palantír, Hipicat, Jazz detect conflicts or similarities
SAFE-COMMIT prevents premature change releases
Continuous Integration
Automatic builds w/ testing to detect conflicts early
SAFE-COMMIT enables partial but safe commits
© Jan Wloka 2009 All Rights reserved. 13

Conclusions and Future Work
SAFE-COMMIT can reduce risk of duplicative work and
merge conflicts:
Compute safely committable changes
Policies of varying strictness using test outcomes
Commit policies can be enforced automatically
Experiments committed significant #changes
Future directions
Change-centric test development/generation
Automated resolution of merge conflicts
© Jan Wloka 2009 All Rights reserved. 14