Add test case for ApiGraph

Author: aibaars

ql/test/library-tests/dataflow/api-graphs/test1.rb

@@ -0,0 +1,11 @@
+MyModule #$ use=moduleImport("MyModule")
+print MyModule.foo #$ use=moduleImport("MyModule").getReturn("foo")
+Kernel.print(e) #$ use=moduleImport("Kernel").getReturn("print")
+Object::Kernel #$ use=moduleImport("Kernel")
+Object::Kernel.print(e)  #$ use=moduleImport("Kernel").getReturn("print")
+begin
+    print MyModule.bar #$ use=moduleImport("MyModule").getReturn("bar")
+rescue AttributeError => e #$ use=moduleImport("AttributeError") // missing because there is no dataflow Node for AttributeError
+    Kernel.print(e)  #$ use=moduleImport("Kernel").getReturn("print")
+end
+Unknown.new.run #$ use=moduleImport("Unknown").instance.getReturn("run")

ql/test/library-tests/dataflow/api-graphs/use.expected

@@ -0,0 +1,2 @@
+| test1.rb:8:28:8:128 | #$ use=moduleImport("AttributeError") // missing because there is no dataflow Node for AttributeError | Missing result:use=moduleImport("AttributeError") |
+| test1.rb:9:22:9:69 | #$ use=moduleImport("Kernel").getReturn("print") | Missing result:use=moduleImport("Kernel").getReturn("print") |

ql/test/library-tests/dataflow/api-graphs/use.ql

@@ -0,0 +1,35 @@
+import ruby
+import codeql_ruby.DataFlow
+import TestUtilities.InlineExpectationsTest
+import codeql_ruby.ApiGraphs
+
+class ApiUseTest extends InlineExpectationsTest {
+  ApiUseTest() { this = "ApiUseTest" }
+
+  override string getARelevantTag() { result = "use" }
+
+  private predicate relevant_node(API::Node a, DataFlow::Node n, Location l) {
+    n = a.getAUse() and
+    l = n.getLocation()
+  }
+
+  override predicate hasActualResult(Location location, string element, string tag, string value) {
+    exists(API::Node a, DataFlow::Node n | relevant_node(a, n, location) |
+      tag = "use" and
+      // Only report the longest path on this line:
+      value =
+        max(API::Node a2, Location l2, DataFlow::Node n2 |
+          relevant_node(a2, n2, l2) and
+          l2.getFile() = location.getFile() and
+          l2.getStartLine() = location.getStartLine()
+        |
+          a2.getPath()
+          order by
+            size(n2.asExpr().getExpr()), a2.getPath().length() desc, a2.getPath() desc
+        ) and
+      element = n.toString()
+    )
+  }
+}
+
+private int size(AstNode n) { result = count(n.getAChild*()) }