Add Java test file for sign analysis

Author: tamasvajk

java/ql/test/library-tests/dataflow/sign-analysis/A.java

@@ -0,0 +1,12 @@
+public class A {
+  int f1(int x, int y) {
+    if (x < 0) {
+      return x; // strictly negative
+    }
+    if (x < y) {
+      return y; // y is strictly positive because of the bound on x above
+    }
+
+    return 0;
+  }
+}

java/ql/test/library-tests/dataflow/sign-analysis/SignAnalysis.expected

@@ -0,0 +1,3 @@
+| A.java:4:14:4:14 | x | negative strictlyNegative |
+| A.java:6:9:6:9 | x | positive |
+| A.java:7:14:7:14 | y | positive strictlyPositive |

java/ql/test/library-tests/dataflow/sign-analysis/SignAnalysis.ql

@@ -0,0 +1,19 @@
+import java
+import semmle.code.java.dataflow.SignAnalysis
+
+string getASignString(Expr i) {
+  positive(i) and
+  result = "positive"
+  or
+  negative(i) and
+  result = "negative"
+  or
+  strictlyPositive(i) and
+  result = "strictlyPositive"
+  or
+  strictlyNegative(i) and
+  result = "strictlyNegative"
+}
+
+from Expr e
+select e, strictconcat(string s | s = getASignString(e) | s, " ")