diff --git a/question/behaviour/deferredcbm/tests/behaviourtype_test.php b/question/behaviour/deferredcbm/tests/behaviourtype_test.php
index a4892e6247e..bfdf933e7a2 100644
--- a/question/behaviour/deferredcbm/tests/behaviourtype_test.php
+++ b/question/behaviour/deferredcbm/tests/behaviourtype_test.php
@@ -139,8 +139,8 @@ class qbehaviour_deferredcbm_type_test extends qbehaviour_walkthrough_test_base
     }
 
     public function test_calculate_bonus() {
-        $this->assertEquals(0.05,  $this->behaviourtype->calculate_bonus(1, 1/2));
-        $this->assertEquals(-0.01, $this->behaviourtype->calculate_bonus(2, 9/10));
-        $this->assertEquals(0,     $this->behaviourtype->calculate_bonus(3, 1));
+        $this->assertEqualsWithDelta(0.05,  $this->behaviourtype->calculate_bonus(1, 1 / 2), question_testcase::GRADE_DELTA);
+        $this->assertEqualsWithDelta(-0.01, $this->behaviourtype->calculate_bonus(2, 9 / 10), question_testcase::GRADE_DELTA);
+        $this->assertEqualsWithDelta(0,     $this->behaviourtype->calculate_bonus(3, 1), question_testcase::GRADE_DELTA);
     }
 }
diff --git a/question/engine/tests/helpers.php b/question/engine/tests/helpers.php
index 13d48b93fff..41147843e73 100644
--- a/question/engine/tests/helpers.php
+++ b/question/engine/tests/helpers.php
@@ -479,6 +479,11 @@ abstract class data_loading_method_test_base extends advanced_testcase {
 
 abstract class question_testcase extends advanced_testcase {
 
+    /**
+     * Tolerance accepted in some unit tests when float operations are involved.
+     */
+    const GRADE_DELTA = 0.00000005;
+
     public function assert($expectation, $compare, $notused = '') {
 
         if (get_class($expectation) === 'question_pattern_expectation') {
diff --git a/question/type/multianswer/tests/question_test.php b/question/type/multianswer/tests/question_test.php
index 9390ad2bced..8bb053a1310 100644
--- a/question/type/multianswer/tests/question_test.php
+++ b/question/type/multianswer/tests/question_test.php
@@ -14,7 +14,6 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
-
 /**
  * Unit tests for the multianswer question definition class.
  *
@@ -199,7 +198,7 @@ class qtype_multianswer_question_test extends advanced_testcase {
                            2 => array('sub1_answer' => 'Owl', 'sub2_answer' => $right),
                           );
         $finalgrade = $question->compute_final_grade($responses, 1);
-        $this->assertEquals(1 / 3 * (1 - 0.2) + 2 / 3 * (1 - 2 * 0.2), $finalgrade);
+        $this->assertEqualsWithDelta(1 / 3 * (1 - 0.2) + 2 / 3 * (1 - 2 * 0.2), $finalgrade, question_testcase::GRADE_DELTA);
 
         // Get subquestion 1 right at 3rd try and subquestion 2 right at 2nd try.
         $responses = array(0 => array('sub1_answer' => 'Dog', 'sub2_answer' => $wrong),
@@ -208,7 +207,7 @@ class qtype_multianswer_question_test extends advanced_testcase {
                            3 => array('sub1_answer' => 'Owl', 'sub2_answer' => $right),
                           );
         $finalgrade = $question->compute_final_grade($responses, 1);
-        $this->assertEquals(1 / 3 * (1 - 2 * 0.2) + 2 / 3 * (1 - 0.2), $finalgrade);
+        $this->assertEqualsWithDelta(1 / 3 * (1 - 2 * 0.2) + 2 / 3 * (1 - 0.2), $finalgrade, question_testcase::GRADE_DELTA);
 
         // Get subquestion 1 right at 4th try and subquestion 2 right at 1st try.
         $responses = array(0 => array('sub1_answer' => 'Dog', 'sub2_answer' => $right),
@@ -217,7 +216,7 @@ class qtype_multianswer_question_test extends advanced_testcase {
                            3 => array('sub1_answer' => 'Owl', 'sub2_answer' => $right),
                           );
         $finalgrade = $question->compute_final_grade($responses, 1);
-        $this->assertEquals(1 / 3 * (1 - 3 * 0.2) + 2 / 3, $finalgrade);
+        $this->assertEqualsWithDelta(1 / 3 * (1 - 3 * 0.2) + 2 / 3, $finalgrade, question_testcase::GRADE_DELTA);
 
         // Get subquestion 1 right at 4th try and subquestion 2 right 3rd try.
         // Subquestion 2 was right at 1st try, but last change is at 3rd try.
@@ -227,7 +226,7 @@ class qtype_multianswer_question_test extends advanced_testcase {
                            3 => array('sub1_answer' => 'Owl', 'sub2_answer' => $right),
                           );
         $finalgrade = $question->compute_final_grade($responses, 1);
-        $this->assertEquals(1 / 3 * (1 - 3 * 0.2) + 2 / 3 * (1 - 2 * 0.2), $finalgrade);
+        $this->assertEqualsWithDelta(1 / 3 * (1 - 3 * 0.2) + 2 / 3 * (1 - 2 * 0.2), $finalgrade, question_testcase::GRADE_DELTA);
 
         // Incomplete responses. Subquestion 1 is right at 4th try and subquestion 2 at 3rd try.
         $responses = array(0 => array('sub1_answer' => 'Dog'),
@@ -236,6 +235,6 @@ class qtype_multianswer_question_test extends advanced_testcase {
                            3 => array('sub1_answer' => 'Owl', 'sub2_answer' => $right),
                           );
         $finalgrade = $question->compute_final_grade($responses, 1);
-        $this->assertEquals(1 / 3 * (1 - 3 * 0.2) + 2 / 3 * (1 - 2 * 0.2), $finalgrade);
+        $this->assertEqualsWithDelta(1 / 3 * (1 - 3 * 0.2) + 2 / 3 * (1 - 2 * 0.2), $finalgrade, question_testcase::GRADE_DELTA);
     }
 }