Why are empty collections of different type equal?

up vote
33
down vote

favorite

What is mechanism below that makes equal different types?

import static org.testng.Assert.assertEquals;

@Test
public void whyThisIsEqual() 
 assertEquals(new HashSet<>(), new ArrayList<>());

edited Sep 6 at 14:26

Konrad Rudolph

384k997551008

asked Sep 6 at 10:16

Bartek Wichowski

434416

add a commentÂ |Â

up vote
33
down vote

favorite

What is mechanism below that makes equal different types?

import static org.testng.Assert.assertEquals;

@Test
public void whyThisIsEqual() 
 assertEquals(new HashSet<>(), new ArrayList<>());

edited Sep 6 at 14:26

Konrad Rudolph

384k997551008

asked Sep 6 at 10:16

Bartek Wichowski

434416

add a commentÂ |Â

up vote
33
down vote

favorite

What is mechanism below that makes equal different types?

import static org.testng.Assert.assertEquals;

@Test
public void whyThisIsEqual() 
 assertEquals(new HashSet<>(), new ArrayList<>());

edited Sep 6 at 14:26

Konrad Rudolph

384k997551008

asked Sep 6 at 10:16

Bartek Wichowski

434416

What is mechanism below that makes equal different types?

import static org.testng.Assert.assertEquals;

@Test
public void whyThisIsEqual() 
 assertEquals(new HashSet<>(), new ArrayList<>());

edited Sep 6 at 14:26

Konrad Rudolph

384k997551008

asked Sep 6 at 10:16

Bartek Wichowski

434416

edited Sep 6 at 14:26

Konrad Rudolph

384k997551008

edited Sep 6 at 14:26

Konrad Rudolph

384k997551008

edited Sep 6 at 14:26

Konrad Rudolph

384k997551008

asked Sep 6 at 10:16

Bartek Wichowski

434416

asked Sep 6 at 10:16

Bartek Wichowski

434416

asked Sep 6 at 10:16

Bartek Wichowski

434416

add a commentÂ |Â

5 Answers
5

active

oldest

votes

up vote
41
down vote

accepted

The assertEquals(Collection<?> actual, Collection<?> expected) documentation says:

Asserts that two collections contain the same elements in the same order. If they do not, an AssertionError is thrown.

Thus the content of the collections will be compared which, in case both the collections are empty, are equal.

edited Sep 6 at 14:46

Aaron

13.8k11434

answered Sep 6 at 10:21

S.K.

1,157616

add a commentÂ |Â

up vote
25
down vote

They are not...

System.out.println(new HashSet<>().equals(new ArrayList<>())); // false

This is specific to testng assertEquals

Looking at the documentation of that method it says:

Asserts that two collections contain the same elements in the same order.

And this is ridiculous to me, a Set does not have an order, per-se.

 Set<String> set = new HashSet<>();
 set.add("hello");
 set.add("from");
 set.add("jug");

 System.out.println(set); // [from, hello, jug]

 IntStream.range(0, 1000).mapToObj(x -> x + "").forEachOrdered(set::add);
 IntStream.range(0, 1000).mapToObj(x -> x + "").forEachOrdered(set::remove);

 System.out.println(set); // [jug, hello, from]

So comparing these against a Collection at some particular point in time would yield interesting results.

Even worse, java-9 Set::of methods implement a randomization internally, so the order (or not the order) will be different from run to run.

edited Sep 6 at 10:43

answered Sep 6 at 10:21

Eugene

59.4k980139

5

I find that a dangerous choice from junit to call assetEquals but not use Object.equals... this lead to "unexpected" behavior like this one.
â€“Â AxelH
Sep 6 at 10:22

@AxelH indeed, I was really not expecting this
â€“Â Eugene
Sep 6 at 10:23

Junit throws an AssertionError here. It is testng which has this behaviour. (I see you edited your answer right when I posted this comment)
â€“Â marstran
Sep 6 at 10:24

@marstran see another edit, I find this a very very weird
â€“Â Eugene
Sep 6 at 10:34

3

@AxelH & Eugene, I agree, this method is misnamed. This should be named something like assertEqualContentsOrdered. It would be useful for comparing a list and a set, in the case that you know that the set is ordered. (There is already assertEqualsNoOrder but it only takes arrays.)
â€“Â Stuart Marks
Sep 6 at 16:37

Â |Â
show 4 more comments

up vote
7
down vote

Testng calls through to a method implemented this way.

 public static void assertEquals(Collection<?> actual, Collection<?> expected, String message)

This is trying to be helpful but is poor for a number of reasons.

Two equals collections can appear to be different.

Set<Integer> a = new HashSet<>();
a.add(82);
a.add(100);
System.err.println(a);
Set<Integer> b = new HashSet<>();
for (int i = 82; i <= 100; i++)
 b.add(i);
for (int i = 83; i <= 99; i++)
 b.remove(i);
System.err.println(b);
System.err.println("a.equals(b) && b.equals(a) is " + (a.equals(b) && b.equals(a)));
assertEquals(a, b, "a <=> b");

and

Set<Integer> a = new HashSet<>();
a.add(100);
a.add(82);
System.err.println(a);
Set<Integer> b = new HashSet<>(32);
b.add(100);
b.add(82);
System.err.println(b);
System.err.println("a.equals(b) && b.equals(a) is " + (a.equals(b) && b.equals(a)));
assertEquals(a, b, "a <=> b");

prints

[82, 100]
[100, 82]
a.equals(b) && b.equals(a) is true
Exception in thread "main" java.lang.AssertionError: a <=> b: Lists differ at element [0]: 100 != 82
 at ....

Two collections can be the same or different depending on how they are compared.

assertEquals(a, (Iterable) b); // passes

assertEquals(a, (Object) b); // passes

assertEquals(Arrays.asList(a), Arrays.asList(b)); // passes

edited Sep 6 at 10:58

answered Sep 6 at 10:26

Peter Lawrey

429k54538912

It's calling this overload: github.com/cbeust/testng/blob/master/src/main/java/org/testng/â€¦
â€“Â marstran
Sep 6 at 10:27

@marstran ouch, so the type of the reference rather than the object changes the behaviour.
â€“Â Peter Lawrey
Sep 6 at 10:30

1

Yep. The overload should have another name imho. Like assertSameElements or something.
â€“Â marstran
Sep 6 at 10:35

@marstran or assertEquals(Object,Object) should check at runtime but even then it's really only good for List not Set
â€“Â Peter Lawrey
Sep 6 at 10:45

3

@AxelH This function is bad other reasons, but that fact that it considers null == null is perfectly consistent with the rest of the language.
â€“Â Todd Sewell
Sep 6 at 11:53

add a commentÂ |Â

up vote
5
down vote

Because for collection only content is compared, not collection type.

Rationale behind it is that often some subclass of collection is returned from tested method and is irrelevant what exactly subclass is used.

answered Sep 6 at 10:19

talex

6,8511544

add a commentÂ |Â

up vote
2
down vote

When I run below code the condition is false.

if( (new HashSet<>()).equals(new ArrayList<>()))
 System.out.println("They are equal");

Hence for assertEquals, it is true that it only checks elements and its order for equality. But for equals it is false.

answered Sep 6 at 10:24

Raj

28912

add a commentÂ |Â

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5 Answers
5

active

oldest

votes

5 Answers
5

active

oldest

votes

up vote
41
down vote

accepted

The assertEquals(Collection<?> actual, Collection<?> expected) documentation says:

Asserts that two collections contain the same elements in the same order. If they do not, an AssertionError is thrown.

Thus the content of the collections will be compared which, in case both the collections are empty, are equal.

edited Sep 6 at 14:46

Aaron

13.8k11434

answered Sep 6 at 10:21

S.K.

1,157616

add a commentÂ |Â

up vote
41
down vote

accepted

The assertEquals(Collection<?> actual, Collection<?> expected) documentation says:

Asserts that two collections contain the same elements in the same order. If they do not, an AssertionError is thrown.

Thus the content of the collections will be compared which, in case both the collections are empty, are equal.

edited Sep 6 at 14:46

Aaron

13.8k11434

answered Sep 6 at 10:21

S.K.

1,157616

add a commentÂ |Â

up vote
41
down vote

accepted

The assertEquals(Collection<?> actual, Collection<?> expected) documentation says:

Asserts that two collections contain the same elements in the same order. If they do not, an AssertionError is thrown.

Thus the content of the collections will be compared which, in case both the collections are empty, are equal.

edited Sep 6 at 14:46

Aaron

13.8k11434

answered Sep 6 at 10:21

S.K.

1,157616

The assertEquals(Collection<?> actual, Collection<?> expected) documentation says:

Asserts that two collections contain the same elements in the same order. If they do not, an AssertionError is thrown.

Thus the content of the collections will be compared which, in case both the collections are empty, are equal.

edited Sep 6 at 14:46

Aaron

13.8k11434

answered Sep 6 at 10:21

S.K.

1,157616

edited Sep 6 at 14:46

Aaron

13.8k11434

edited Sep 6 at 14:46

Aaron

13.8k11434

edited Sep 6 at 14:46

Aaron

13.8k11434

answered Sep 6 at 10:21

S.K.

1,157616

answered Sep 6 at 10:21

S.K.

1,157616

answered Sep 6 at 10:21

S.K.

1,157616

add a commentÂ |Â

up vote
25
down vote

They are not...

System.out.println(new HashSet<>().equals(new ArrayList<>())); // false

This is specific to testng assertEquals

Looking at the documentation of that method it says:

Asserts that two collections contain the same elements in the same order.

And this is ridiculous to me, a Set does not have an order, per-se.

 Set<String> set = new HashSet<>();
 set.add("hello");
 set.add("from");
 set.add("jug");

 System.out.println(set); // [from, hello, jug]

 IntStream.range(0, 1000).mapToObj(x -> x + "").forEachOrdered(set::add);
 IntStream.range(0, 1000).mapToObj(x -> x + "").forEachOrdered(set::remove);

 System.out.println(set); // [jug, hello, from]

So comparing these against a Collection at some particular point in time would yield interesting results.

Even worse, java-9 Set::of methods implement a randomization internally, so the order (or not the order) will be different from run to run.

edited Sep 6 at 10:43

answered Sep 6 at 10:21

Eugene

59.4k980139

5

I find that a dangerous choice from junit to call assetEquals but not use Object.equals... this lead to "unexpected" behavior like this one.
â€“Â AxelH
Sep 6 at 10:22

@AxelH indeed, I was really not expecting this
â€“Â Eugene
Sep 6 at 10:23

Junit throws an AssertionError here. It is testng which has this behaviour. (I see you edited your answer right when I posted this comment)
â€“Â marstran
Sep 6 at 10:24

@marstran see another edit, I find this a very very weird
â€“Â Eugene
Sep 6 at 10:34

3

@AxelH & Eugene, I agree, this method is misnamed. This should be named something like assertEqualContentsOrdered. It would be useful for comparing a list and a set, in the case that you know that the set is ordered. (There is already assertEqualsNoOrder but it only takes arrays.)
â€“Â Stuart Marks
Sep 6 at 16:37

Â |Â
show 4 more comments

up vote
25
down vote

They are not...

System.out.println(new HashSet<>().equals(new ArrayList<>())); // false

This is specific to testng assertEquals

Looking at the documentation of that method it says:

Asserts that two collections contain the same elements in the same order.

And this is ridiculous to me, a Set does not have an order, per-se.

 Set<String> set = new HashSet<>();
 set.add("hello");
 set.add("from");
 set.add("jug");

 System.out.println(set); // [from, hello, jug]

 IntStream.range(0, 1000).mapToObj(x -> x + "").forEachOrdered(set::add);
 IntStream.range(0, 1000).mapToObj(x -> x + "").forEachOrdered(set::remove);

 System.out.println(set); // [jug, hello, from]

So comparing these against a Collection at some particular point in time would yield interesting results.

Even worse, java-9 Set::of methods implement a randomization internally, so the order (or not the order) will be different from run to run.

edited Sep 6 at 10:43

answered Sep 6 at 10:21

Eugene

59.4k980139

5

I find that a dangerous choice from junit to call assetEquals but not use Object.equals... this lead to "unexpected" behavior like this one.
â€“Â AxelH
Sep 6 at 10:22

@AxelH indeed, I was really not expecting this
â€“Â Eugene
Sep 6 at 10:23

Junit throws an AssertionError here. It is testng which has this behaviour. (I see you edited your answer right when I posted this comment)
â€“Â marstran
Sep 6 at 10:24

@marstran see another edit, I find this a very very weird
â€“Â Eugene
Sep 6 at 10:34

3

@AxelH & Eugene, I agree, this method is misnamed. This should be named something like assertEqualContentsOrdered. It would be useful for comparing a list and a set, in the case that you know that the set is ordered. (There is already assertEqualsNoOrder but it only takes arrays.)
â€“Â Stuart Marks
Sep 6 at 16:37

Â |Â
show 4 more comments

up vote
25
down vote

They are not...

System.out.println(new HashSet<>().equals(new ArrayList<>())); // false

This is specific to testng assertEquals

Looking at the documentation of that method it says:

Asserts that two collections contain the same elements in the same order.

And this is ridiculous to me, a Set does not have an order, per-se.

 Set<String> set = new HashSet<>();
 set.add("hello");
 set.add("from");
 set.add("jug");

 System.out.println(set); // [from, hello, jug]

 IntStream.range(0, 1000).mapToObj(x -> x + "").forEachOrdered(set::add);
 IntStream.range(0, 1000).mapToObj(x -> x + "").forEachOrdered(set::remove);

 System.out.println(set); // [jug, hello, from]

So comparing these against a Collection at some particular point in time would yield interesting results.

Even worse, java-9 Set::of methods implement a randomization internally, so the order (or not the order) will be different from run to run.

edited Sep 6 at 10:43

answered Sep 6 at 10:21

Eugene

59.4k980139

They are not...

System.out.println(new HashSet<>().equals(new ArrayList<>())); // false

This is specific to testng assertEquals

Looking at the documentation of that method it says:

Asserts that two collections contain the same elements in the same order.

And this is ridiculous to me, a Set does not have an order, per-se.

 Set<String> set = new HashSet<>();
 set.add("hello");
 set.add("from");
 set.add("jug");

 System.out.println(set); // [from, hello, jug]

 IntStream.range(0, 1000).mapToObj(x -> x + "").forEachOrdered(set::add);
 IntStream.range(0, 1000).mapToObj(x -> x + "").forEachOrdered(set::remove);

 System.out.println(set); // [jug, hello, from]

So comparing these against a Collection at some particular point in time would yield interesting results.

Even worse, java-9 Set::of methods implement a randomization internally, so the order (or not the order) will be different from run to run.

edited Sep 6 at 10:43

answered Sep 6 at 10:21

Eugene

59.4k980139

edited Sep 6 at 10:43

answered Sep 6 at 10:21

Eugene

59.4k980139

answered Sep 6 at 10:21

Eugene

59.4k980139

answered Sep 6 at 10:21

Eugene

59.4k980139

5

I find that a dangerous choice from junit to call assetEquals but not use Object.equals... this lead to "unexpected" behavior like this one.
â€“Â AxelH
Sep 6 at 10:22

@AxelH indeed, I was really not expecting this
â€“Â Eugene
Sep 6 at 10:23

Junit throws an AssertionError here. It is testng which has this behaviour. (I see you edited your answer right when I posted this comment)
â€“Â marstran
Sep 6 at 10:24

@marstran see another edit, I find this a very very weird
â€“Â Eugene
Sep 6 at 10:34

3

@AxelH & Eugene, I agree, this method is misnamed. This should be named something like assertEqualContentsOrdered. It would be useful for comparing a list and a set, in the case that you know that the set is ordered. (There is already assertEqualsNoOrder but it only takes arrays.)
â€“Â Stuart Marks
Sep 6 at 16:37

Â |Â
show 4 more comments

5

I find that a dangerous choice from junit to call assetEquals but not use Object.equals... this lead to "unexpected" behavior like this one.
â€“Â AxelH
Sep 6 at 10:22

@AxelH indeed, I was really not expecting this
â€“Â Eugene
Sep 6 at 10:23

Junit throws an AssertionError here. It is testng which has this behaviour. (I see you edited your answer right when I posted this comment)
â€“Â marstran
Sep 6 at 10:24

@marstran see another edit, I find this a very very weird
â€“Â Eugene
Sep 6 at 10:34

3

@AxelH & Eugene, I agree, this method is misnamed. This should be named something like assertEqualContentsOrdered. It would be useful for comparing a list and a set, in the case that you know that the set is ordered. (There is already assertEqualsNoOrder but it only takes arrays.)
â€“Â Stuart Marks
Sep 6 at 16:37

I find that a dangerous choice from junit to call assetEquals but not use Object.equals... this lead to "unexpected" behavior like this one.
â€“Â AxelH
Sep 6 at 10:22

@AxelH indeed, I was really not expecting this
â€“Â Eugene
Sep 6 at 10:23

Junit throws an AssertionError here. It is testng which has this behaviour. (I see you edited your answer right when I posted this comment)
â€“Â marstran
Sep 6 at 10:24

@marstran see another edit, I find this a very very weird
â€“Â Eugene
Sep 6 at 10:34

@AxelH & Eugene, I agree, this method is misnamed. This should be named something like assertEqualContentsOrdered. It would be useful for comparing a list and a set, in the case that you know that the set is ordered. (There is already assertEqualsNoOrder but it only takes arrays.)
â€“Â Stuart Marks
Sep 6 at 16:37

Â |Â
show 4 more comments

up vote
7
down vote

Testng calls through to a method implemented this way.

 public static void assertEquals(Collection<?> actual, Collection<?> expected, String message)

This is trying to be helpful but is poor for a number of reasons.

Two equals collections can appear to be different.

Set<Integer> a = new HashSet<>();
a.add(82);
a.add(100);
System.err.println(a);
Set<Integer> b = new HashSet<>();
for (int i = 82; i <= 100; i++)
 b.add(i);
for (int i = 83; i <= 99; i++)
 b.remove(i);
System.err.println(b);
System.err.println("a.equals(b) && b.equals(a) is " + (a.equals(b) && b.equals(a)));
assertEquals(a, b, "a <=> b");

and

Set<Integer> a = new HashSet<>();
a.add(100);
a.add(82);
System.err.println(a);
Set<Integer> b = new HashSet<>(32);
b.add(100);
b.add(82);
System.err.println(b);
System.err.println("a.equals(b) && b.equals(a) is " + (a.equals(b) && b.equals(a)));
assertEquals(a, b, "a <=> b");

prints

[82, 100]
[100, 82]
a.equals(b) && b.equals(a) is true
Exception in thread "main" java.lang.AssertionError: a <=> b: Lists differ at element [0]: 100 != 82
 at ....

Two collections can be the same or different depending on how they are compared.

assertEquals(a, (Iterable) b); // passes

assertEquals(a, (Object) b); // passes

assertEquals(Arrays.asList(a), Arrays.asList(b)); // passes

edited Sep 6 at 10:58

answered Sep 6 at 10:26

Peter Lawrey

429k54538912

It's calling this overload: github.com/cbeust/testng/blob/master/src/main/java/org/testng/â€¦
â€“Â marstran
Sep 6 at 10:27

@marstran ouch, so the type of the reference rather than the object changes the behaviour.
â€“Â Peter Lawrey
Sep 6 at 10:30

1

Yep. The overload should have another name imho. Like assertSameElements or something.
â€“Â marstran
Sep 6 at 10:35

@marstran or assertEquals(Object,Object) should check at runtime but even then it's really only good for List not Set
â€“Â Peter Lawrey
Sep 6 at 10:45

3

@AxelH This function is bad other reasons, but that fact that it considers null == null is perfectly consistent with the rest of the language.
â€“Â Todd Sewell
Sep 6 at 11:53

add a commentÂ |Â

up vote
7
down vote

Testng calls through to a method implemented this way.

 public static void assertEquals(Collection<?> actual, Collection<?> expected, String message)

This is trying to be helpful but is poor for a number of reasons.

Two equals collections can appear to be different.

Set<Integer> a = new HashSet<>();
a.add(82);
a.add(100);
System.err.println(a);
Set<Integer> b = new HashSet<>();
for (int i = 82; i <= 100; i++)
 b.add(i);
for (int i = 83; i <= 99; i++)
 b.remove(i);
System.err.println(b);
System.err.println("a.equals(b) && b.equals(a) is " + (a.equals(b) && b.equals(a)));
assertEquals(a, b, "a <=> b");

and

Set<Integer> a = new HashSet<>();
a.add(100);
a.add(82);
System.err.println(a);
Set<Integer> b = new HashSet<>(32);
b.add(100);
b.add(82);
System.err.println(b);
System.err.println("a.equals(b) && b.equals(a) is " + (a.equals(b) && b.equals(a)));
assertEquals(a, b, "a <=> b");

prints

[82, 100]
[100, 82]
a.equals(b) && b.equals(a) is true
Exception in thread "main" java.lang.AssertionError: a <=> b: Lists differ at element [0]: 100 != 82
 at ....

Two collections can be the same or different depending on how they are compared.

assertEquals(a, (Iterable) b); // passes

assertEquals(a, (Object) b); // passes

assertEquals(Arrays.asList(a), Arrays.asList(b)); // passes

edited Sep 6 at 10:58

answered Sep 6 at 10:26

Peter Lawrey

429k54538912

It's calling this overload: github.com/cbeust/testng/blob/master/src/main/java/org/testng/â€¦
â€“Â marstran
Sep 6 at 10:27

@marstran ouch, so the type of the reference rather than the object changes the behaviour.
â€“Â Peter Lawrey
Sep 6 at 10:30

1

Yep. The overload should have another name imho. Like assertSameElements or something.
â€“Â marstran
Sep 6 at 10:35

@marstran or assertEquals(Object,Object) should check at runtime but even then it's really only good for List not Set
â€“Â Peter Lawrey
Sep 6 at 10:45

3

@AxelH This function is bad other reasons, but that fact that it considers null == null is perfectly consistent with the rest of the language.
â€“Â Todd Sewell
Sep 6 at 11:53

add a commentÂ |Â

up vote
7
down vote

Testng calls through to a method implemented this way.

 public static void assertEquals(Collection<?> actual, Collection<?> expected, String message)

This is trying to be helpful but is poor for a number of reasons.

Two equals collections can appear to be different.

Set<Integer> a = new HashSet<>();
a.add(82);
a.add(100);
System.err.println(a);
Set<Integer> b = new HashSet<>();
for (int i = 82; i <= 100; i++)
 b.add(i);
for (int i = 83; i <= 99; i++)
 b.remove(i);
System.err.println(b);
System.err.println("a.equals(b) && b.equals(a) is " + (a.equals(b) && b.equals(a)));
assertEquals(a, b, "a <=> b");

and

Set<Integer> a = new HashSet<>();
a.add(100);
a.add(82);
System.err.println(a);
Set<Integer> b = new HashSet<>(32);
b.add(100);
b.add(82);
System.err.println(b);
System.err.println("a.equals(b) && b.equals(a) is " + (a.equals(b) && b.equals(a)));
assertEquals(a, b, "a <=> b");

prints

[82, 100]
[100, 82]
a.equals(b) && b.equals(a) is true
Exception in thread "main" java.lang.AssertionError: a <=> b: Lists differ at element [0]: 100 != 82
 at ....

Two collections can be the same or different depending on how they are compared.

assertEquals(a, (Iterable) b); // passes

assertEquals(a, (Object) b); // passes

assertEquals(Arrays.asList(a), Arrays.asList(b)); // passes

edited Sep 6 at 10:58

answered Sep 6 at 10:26

Peter Lawrey

429k54538912

Testng calls through to a method implemented this way.

 public static void assertEquals(Collection<?> actual, Collection<?> expected, String message)

This is trying to be helpful but is poor for a number of reasons.

Two equals collections can appear to be different.

Set<Integer> a = new HashSet<>();
a.add(82);
a.add(100);
System.err.println(a);
Set<Integer> b = new HashSet<>();
for (int i = 82; i <= 100; i++)
 b.add(i);
for (int i = 83; i <= 99; i++)
 b.remove(i);
System.err.println(b);
System.err.println("a.equals(b) && b.equals(a) is " + (a.equals(b) && b.equals(a)));
assertEquals(a, b, "a <=> b");

and

Set<Integer> a = new HashSet<>();
a.add(100);
a.add(82);
System.err.println(a);
Set<Integer> b = new HashSet<>(32);
b.add(100);
b.add(82);
System.err.println(b);
System.err.println("a.equals(b) && b.equals(a) is " + (a.equals(b) && b.equals(a)));
assertEquals(a, b, "a <=> b");

prints

[82, 100]
[100, 82]
a.equals(b) && b.equals(a) is true
Exception in thread "main" java.lang.AssertionError: a <=> b: Lists differ at element [0]: 100 != 82
 at ....

Two collections can be the same or different depending on how they are compared.

assertEquals(a, (Iterable) b); // passes

assertEquals(a, (Object) b); // passes

assertEquals(Arrays.asList(a), Arrays.asList(b)); // passes

edited Sep 6 at 10:58

answered Sep 6 at 10:26

Peter Lawrey

429k54538912

edited Sep 6 at 10:58

answered Sep 6 at 10:26

Peter Lawrey

429k54538912

answered Sep 6 at 10:26

Peter Lawrey

429k54538912

answered Sep 6 at 10:26

Peter Lawrey

429k54538912

It's calling this overload: github.com/cbeust/testng/blob/master/src/main/java/org/testng/â€¦
â€“Â marstran
Sep 6 at 10:27

@marstran ouch, so the type of the reference rather than the object changes the behaviour.
â€“Â Peter Lawrey
Sep 6 at 10:30

1

Yep. The overload should have another name imho. Like assertSameElements or something.
â€“Â marstran
Sep 6 at 10:35

@marstran or assertEquals(Object,Object) should check at runtime but even then it's really only good for List not Set
â€“Â Peter Lawrey
Sep 6 at 10:45

3

@AxelH This function is bad other reasons, but that fact that it considers null == null is perfectly consistent with the rest of the language.
â€“Â Todd Sewell
Sep 6 at 11:53

add a commentÂ |Â

It's calling this overload: github.com/cbeust/testng/blob/master/src/main/java/org/testng/â€¦
â€“Â marstran
Sep 6 at 10:27

@marstran ouch, so the type of the reference rather than the object changes the behaviour.
â€“Â Peter Lawrey
Sep 6 at 10:30

1

Yep. The overload should have another name imho. Like assertSameElements or something.
â€“Â marstran
Sep 6 at 10:35

@marstran or assertEquals(Object,Object) should check at runtime but even then it's really only good for List not Set
â€“Â Peter Lawrey
Sep 6 at 10:45

3

@AxelH This function is bad other reasons, but that fact that it considers null == null is perfectly consistent with the rest of the language.
â€“Â Todd Sewell
Sep 6 at 11:53

It's calling this overload: github.com/cbeust/testng/blob/master/src/main/java/org/testng/â€¦
â€“Â marstran
Sep 6 at 10:27

@marstran ouch, so the type of the reference rather than the object changes the behaviour.
â€“Â Peter Lawrey
Sep 6 at 10:30

Yep. The overload should have another name imho. Like assertSameElements or something.
â€“Â marstran
Sep 6 at 10:35

@marstran or assertEquals(Object,Object) should check at runtime but even then it's really only good for List not Set
â€“Â Peter Lawrey
Sep 6 at 10:45

@AxelH This function is bad other reasons, but that fact that it considers null == null is perfectly consistent with the rest of the language.
â€“Â Todd Sewell
Sep 6 at 11:53

add a commentÂ |Â

up vote
5
down vote

Because for collection only content is compared, not collection type.

Rationale behind it is that often some subclass of collection is returned from tested method and is irrelevant what exactly subclass is used.

answered Sep 6 at 10:19

talex

6,8511544

add a commentÂ |Â

up vote
5
down vote

Because for collection only content is compared, not collection type.

Rationale behind it is that often some subclass of collection is returned from tested method and is irrelevant what exactly subclass is used.

answered Sep 6 at 10:19

talex

6,8511544

add a commentÂ |Â

up vote
5
down vote

Because for collection only content is compared, not collection type.

Rationale behind it is that often some subclass of collection is returned from tested method and is irrelevant what exactly subclass is used.

answered Sep 6 at 10:19

talex

6,8511544

Because for collection only content is compared, not collection type.

Rationale behind it is that often some subclass of collection is returned from tested method and is irrelevant what exactly subclass is used.

answered Sep 6 at 10:19

talex

6,8511544

answered Sep 6 at 10:19

talex

6,8511544

answered Sep 6 at 10:19

talex

6,8511544

answered Sep 6 at 10:19

talex

6,8511544

add a commentÂ |Â

up vote
2
down vote

When I run below code the condition is false.

if( (new HashSet<>()).equals(new ArrayList<>()))
 System.out.println("They are equal");

Hence for assertEquals, it is true that it only checks elements and its order for equality. But for equals it is false.

answered Sep 6 at 10:24

Raj

28912

add a commentÂ |Â

up vote
2
down vote

When I run below code the condition is false.

if( (new HashSet<>()).equals(new ArrayList<>()))
 System.out.println("They are equal");

Hence for assertEquals, it is true that it only checks elements and its order for equality. But for equals it is false.

answered Sep 6 at 10:24

Raj

28912

add a commentÂ |Â

up vote
2
down vote

When I run below code the condition is false.

if( (new HashSet<>()).equals(new ArrayList<>()))
 System.out.println("They are equal");

Hence for assertEquals, it is true that it only checks elements and its order for equality. But for equals it is false.

answered Sep 6 at 10:24

Raj

28912

When I run below code the condition is false.

if( (new HashSet<>()).equals(new ArrayList<>()))
 System.out.println("They are equal");

Hence for assertEquals, it is true that it only checks elements and its order for equality. But for equals it is false.

answered Sep 6 at 10:24

Raj

28912

answered Sep 6 at 10:24

Raj

28912

answered Sep 6 at 10:24

Raj

28912

answered Sep 6 at 10:24

Raj

28912

add a commentÂ |Â

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