Tests: Add "only/module-then-test.js" test fixture

Ref qunitjs#1645.
Ref qunitjs#1658.

src/module.js

@@ -134,10 +134,14 @@ export default function module( name, options, executeNow ) {
 
 module.only = function( ...args ) {
 	if ( !focused ) {
+
+		// Upon the first module.only() call,
+		// delete any and all previously registered modules and tests.
 		config.modules.length = 0;
 		config.queue.length = 0;
 
-		// aggressively ignore any direct tests in "outer" nested modules
+		// Ignore any tests declared after this block within the same
+		// module parent. https://github.com/qunitjs/qunit/issues/1645
 		config.currentModule.ignored = true;
 	}
 

test/cli/cli-main.js

@@ -655,6 +655,16 @@ CALLBACK: done`;
 			assert.equal( execution.stdout, expectedOutput[ command ] );
 		} );
 
+		QUnit.test( "module followed by test", async assert => {
+
+			const command = "qunit only/module-then-test.js";
+			const execution = await execute( command );
+
+			assert.equal( execution.code, 0 );
+			assert.equal( execution.stderr, "" );
+			assert.equal( execution.stdout, expectedOutput[ command ] );
+		} );
+
 		QUnit.test( "flat modules", async assert => {
 
 			const command = "qunit only/module-flat.js";

test/cli/fixtures/expected/tap-outputs.js

@@ -319,6 +319,16 @@ ok 6 module E > test E
 # todo 1
 # fail 0`,
 
+	"qunit only/module-then-test.js":
+`TAP version 13
+ok 1 module A > module B > test B
+1..2
+# pass 2
+# skip 0
+# todo 0
+# fail 0`,
+
+
 	"qunit only/module-flat.js":
 `TAP version 13
 not ok 1 # TODO module B > test B

test/cli/fixtures/only/module-then-test.js

@@ -0,0 +1,16 @@
+// https://github.com/qunitjs/qunit/issues/1645
+QUnit.module( "module A", function() {
+	QUnit.test( "test A1", function( assert ) {
+		assert.true( false, "not run" );
+	} );
+
+	QUnit.module.only( "module B", function() {
+		QUnit.test( "test B", function( assert ) {
+			assert.true( true, "run" );
+		} );
+	} );
+
+	QUnit.test( "test A2", function( assert ) {
+		assert.true( false, "not run" );
+	} );
+} );

test/cli/fixtures/only/module.js

@@ -26,10 +26,6 @@ QUnit.module( "module B", function() {
 		} );
 	} );
 
-	QUnit.test( "test with the only-module as its peer", function( assert ) {
-		assert.true( false, "this test should not run" );
-	} );
-
 	QUnit.module( "This also should not run", function() {
 		QUnit.test( "normal test", function( assert ) {
 			assert.true( false, "this test should not run" );