fix: Invert the substring match type to match the condition value as a substring of the user attribute value (#224)

Author: mikeproeng37

core-api/src/main/java/com/optimizely/ab/config/audience/match/SubstringMatch.java

@@ -24,10 +24,15 @@ protected SubstringMatch(String value) {
         this.value = value;
     }
 
+    /**
+     * This matches the same substring matching logic in the Web client.
+     * @param attributeValue
+     * @return true/false if the user attribute string value contains the condition string value
+     */
     public @Nullable
     Boolean eval(Object attributeValue) {
         try {
-            return value.contains(convert(attributeValue));
+            return convert(attributeValue).contains(value);
         }
         catch (Exception e) {
             MatchType.logger.error("Substring match failed ", e);

core-api/src/test/java/com/optimizely/ab/config/audience/AudienceConditionEvaluationTest.java

@@ -310,7 +310,17 @@ public void ltMatchConditionEvaluatesNull() throws Exception {
      */
     @Test
     public void substringMatchConditionEvaluatesTrue() throws Exception {
-        UserAttribute testInstanceString = new UserAttribute("browser_type",  "custom_attribute","substring", "chrome1");
+        UserAttribute testInstanceString = new UserAttribute("browser_type",  "custom_attribute","substring", "chrome");
+        assertTrue(testInstanceString.evaluate(testUserAttributes));
+    }
+
+    /**
+     * Verify that UserAttribute.evaluate for SUBSTRING match type returns true if the
+     * UserAttribute's value is a substring of the condition's value.
+     */
+    @Test
+    public void substringMatchConditionPartialMatchEvaluatesTrue() throws Exception {
+        UserAttribute testInstanceString = new UserAttribute("browser_type",  "custom_attribute","substring", "chro");
         assertTrue(testInstanceString.evaluate(testUserAttributes));
     }
 
@@ -320,7 +330,7 @@ public void substringMatchConditionEvaluatesTrue() throws Exception {
      */
     @Test
     public void substringMatchConditionEvaluatesFalse() throws Exception {
-        UserAttribute testInstanceString = new UserAttribute("browser_type",  "custom_attribute","substring", "chr");
+        UserAttribute testInstanceString = new UserAttribute("browser_type",  "custom_attribute","substring", "chr0me");
         assertFalse(testInstanceString.evaluate(testUserAttributes));
     }