Make sure role group delegates .WHY to its default candidate

This required to remove tests which were testing for `Role.WHY`
returning `Nil`. But as was suggested in this comment:

rakudo/rakudo#3549 (comment)

the tests were needed to ensure that a documentation comment is attached
to a particular parametric role, not to its group. But since
rakudo/rakudo#3549 makes `.WHY` delegate to the default candidate, these
tests doesn't make sense anymore. Instead why-both.t now makes sure what
we get from a role group is the same object we get from the default
candidate.

Alongside with the essential changes, also unified all tests with regard
to use of idential test assertion subs. They all now are `subtest`
based.

S26-documentation/block-leading.t

@@ -1,24 +1,26 @@
 use v6;
 use Test;
-plan 335;
+plan 64;
 
 my $pod_index = 0;
 
 # Test that we get the values we expect from WHY.contents, WHY.leading,
 # WHY.trailing, and that WHY.WHEREFORE is the appropriate thing
 # Also checks the $=pod object is set appropriately.
-# XXX we need to be able to affect the test level (like Test::Builder::Level
-#     in Perl) so that failures point at the caller
+#?DOES 1
 sub test-leading($thing, $value) is test-assertion {
-    is $thing.WHY.?contents, $value, $value  ~ ' - contents';
-    is $thing.WHY.?WHEREFORE.^name, $thing.^name, $value ~ ' - WHEREFORE';
-    is $thing.WHY.?leading, $value, $value ~ ' - leading';
-    ok !$thing.WHY.?trailing.defined, $value ~ ' - no trailing';
-    is ~$thing.WHY, $value, $value ~ ' - stringifies correctly';
-
-    is $=pod[$pod_index].?WHEREFORE.^name,$thing.^name, "\$=pod $value - WHEREFORE";
-    is ~$=pod[$pod_index], $value, "\$=pod $value";
-    $pod_index++;
+    subtest $thing.^name => {
+        plan 7;
+        is $thing.WHY.?contents, $value, $value  ~ ' - contents';
+        is $thing.WHY.?WHEREFORE.^name, $thing.^name, $value ~ ' - WHEREFORE';
+        is $thing.WHY.?leading, $value, $value ~ ' - leading';
+        ok !$thing.WHY.?trailing.defined, $value ~ ' - no trailing';
+        is ~$thing.WHY, $value, $value ~ ' - stringifies correctly';
+
+        is $=pod[$pod_index].?WHEREFORE.^name,$thing.^name, "\$=pod $value - WHEREFORE";
+        is ~$=pod[$pod_index], $value, "\$=pod $value";
+        $pod_index++;
+    }
 }
 
 
@@ -192,7 +194,6 @@ role Boxer {
 
 {
     my $method = Boxer.^lookup('actor');
-    ok !Boxer.WHY.defined, q{Role group's WHY should not be defined};
     test-leading(Boxer.HOW.candidates(Boxer)[0], 'Are you talking to me?');
     test-leading($method, 'Robert De Niro');
 }

S26-documentation/block-trailing.t

@@ -1,12 +1,12 @@
 use v6;
 use Test;
-plan 52;
+plan 51;
 
 my $pod_index = 0;
 
 #?DOES 1
 sub test-trailing($thing, $value) is test-assertion {
-    subtest $thing.^name, {
+    subtest $thing.^name => {
         plan 7;
         is $thing.WHY.?contents, $value, $value  ~ ' - contents';
         is $thing.WHY.?WHEREFORE.^name, $thing.^name, $value ~ ' - WHEREFORE';
@@ -189,7 +189,6 @@ role Boxer {
 
 {
     my $method = Boxer.^lookup('actor');
-    ok !Boxer.WHY.defined, q{Role group's WHY should not be defined};
     test-trailing(Boxer.HOW.candidates(Boxer)[0], 'Are you talking to me?');
     test-trailing($method, 'Robert De Niro');
 }

S26-documentation/why-both.t

@@ -1,22 +1,26 @@
 use v6;
 use Test;
-plan 291;
+plan 58;
 
 my $pod_index = 0;
 
+#?DOES 1
 sub test-both($thing, $leading, $trailing) is test-assertion {
-    my $combined = "$leading\n$trailing";
-    my $name     = "$leading\\n$trailing";
-
-    is $thing.WHY.?contents, $combined, $name  ~ ' - contents';
-    is $thing.WHY.?WHEREFORE.^name, $thing.^name, $name ~ ' - WHEREFORE';
-    is $thing.WHY.?leading, $leading, $name ~ ' - trailing';
-    is $thing.WHY.?trailing, $trailing, $name ~ ' - trailing';
-    is ~$thing.WHY, $combined, $name ~ ' - stringifies correctly';
-
-    is $=pod[$pod_index].?WHEREFORE.^name, $thing.^name, "\$=pod $name - WHEREFORE";
-    is ~$=pod[$pod_index], $combined, "\$=pod $name";
-    $pod_index++;
+    subtest $thing.^name => {
+        plan 7;
+        my $combined = "$leading\n$trailing";
+        my $name     = "$leading\\n$trailing";
+
+        is $thing.WHY.?contents, $combined, $name  ~ ' - contents';
+        is $thing.WHY.?WHEREFORE.^name, $thing.^name, $name ~ ' - WHEREFORE';
+        is $thing.WHY.?leading, $leading, $name ~ ' - trailing';
+        is $thing.WHY.?trailing, $trailing, $name ~ ' - trailing';
+        is ~$thing.WHY, $combined, $name ~ ' - stringifies correctly';
+
+        is $=pod[$pod_index].?WHEREFORE.^name, $thing.^name, "\$=pod $name - WHEREFORE";
+        is ~$=pod[$pod_index], $combined, "\$=pod $name";
+        $pod_index++;
+    }
 }
 
 #| simple case
@@ -74,7 +78,7 @@ my $roar-method = Sheep.^lookup('roar');
 
 test-both($roar-method, 'not too scary', '...unless you fear sheep!');
 
-#| trailing space here  
+#| trailing space here
 sub third {}
 #=    leading space here
 
@@ -141,11 +145,17 @@ role Boxer {
     #= he's an actor
 }
 
+#| I'm not talkative
+role Boxer[::T] {
+#= and this is OK
+}
+
 {
     my $method = Boxer.^lookup('actor');
-    ok !Boxer.WHY.defined, q{Role group's WHY should not be defined};
     test-both(Boxer.HOW.candidates(Boxer)[0], 'Are you talking to me?', 'I said, are you talking to me?');
+    ok Boxer.WHY =:= Boxer.^candidates[0].WHY, q{Role group's WHY is the one of its default candidate};
     test-both($method, 'Robert De Niro', q{he's an actor});
+    test-both(Boxer.HOW.candidates(Boxer)[1], q{I'm not talkative}, q{and this is OK});
 }
 
 class C {

S26-documentation/why-leading.t

@@ -1,24 +1,26 @@
 use v6;
 use Test;
-plan 356;
+plan 67;
 
 my $pod_index = 0;
 
 # Test that we get the values we expect from WHY.contents, WHY.leading,
 # WHY.trailing, and that WHY.WHEREFORE is the appropriate thing
 # Also checks the $=pod object is set appropriately.
-# XXX we need to be able to affect the test level (like Test::Builder::Level
-#     in Perl) so that failures point at the caller
+#?DOES 1
 sub test-leading($thing, $value) is test-assertion {
-    is $thing.WHY.?contents, $value, $value  ~ ' - contents';
-    is $thing.WHY.?WHEREFORE.^name, $thing.^name, $value ~ ' - WHEREFORE';
-    is $thing.WHY.?leading, $value, $value ~ ' - leading';
-    ok !$thing.WHY.?trailing.defined, $value ~ ' - no trailing';
-    is ~$thing.WHY, $value, $value ~ ' - stringifies correctly';
-
-    is $=pod[$pod_index].?WHEREFORE.^name, $thing.^name, "\$=pod $value - WHEREFORE";
-    is ~$=pod[$pod_index], $value, "\$=pod $value";
-    $pod_index++;
+    subtest $thing.^name => {
+        plan 7;
+        is $thing.WHY.?contents, $value, $value  ~ ' - contents';
+        is $thing.WHY.?WHEREFORE.^name, $thing.^name, $value ~ ' - WHEREFORE';
+        is $thing.WHY.?leading, $value, $value ~ ' - leading';
+        ok !$thing.WHY.?trailing.defined, $value ~ ' - no trailing';
+        is ~$thing.WHY, $value, $value ~ ' - stringifies correctly';
+
+        is $=pod[$pod_index].?WHEREFORE.^name, $thing.^name, "\$=pod $value - WHEREFORE";
+        is ~$=pod[$pod_index], $value, "\$=pod $value";
+        $pod_index++;
+    }
 }
 
 
@@ -184,7 +186,6 @@ role Boxer {
 
 {
     my $method = Boxer.^lookup('actor');
-    ok !Boxer.WHY.defined, q{Role group's WHY should not be defined};
     test-leading(Boxer.HOW.candidates(Boxer)[0], 'Are you talking to me?');
     test-leading($method, 'Robert De Niro');
 }

S26-documentation/why-trailing.t

@@ -1,12 +1,12 @@
 use v6;
 use Test;
-plan 56;
+plan 55;
 
 my $pod_index = 0;
 
 #?DOES 1
 sub test-trailing($thing, $value) is test-assertion {
-    subtest $thing.^name, {
+    subtest $thing.^name => {
         plan 7;
         is $thing.WHY.?contents, $value, $value  ~ ' - contents';
         is $thing.WHY.?WHEREFORE.^name, $thing.^name, $value ~ ' - WHEREFORE';
@@ -183,7 +183,6 @@ role Boxer {
 
 {
     my $method = Boxer.^lookup('actor');
-    ok !Boxer.WHY.defined, q{Role group's WHY should not be defined};
     test-trailing(Boxer.HOW.candidates(Boxer)[0], 'Are you talking to me?');
     test-trailing($method, 'Robert De Niro');
 }