Use $(...) instead of `...` in test scripts

tests/common_infra.sh

@@ -72,7 +72,7 @@ X52_MFD_LINE_2_CLR_INDEX='00dc'
 find_programs()
 {
     # Tests and distcheck do not work on OSX, skip the tests
-    if [[ `uname -s` == [Dd]arwin* ]]
+    if [[ $(uname -s) == [Dd]arwin* ]]
     then
         echo "1..0 # skip Tests not supported on OSX"
         exit 0

tests/libx52/test_brightness

@@ -16,7 +16,7 @@ brightness_test()
     local index="\$X52_${unit}_BRIGHTNESS_INDEX"
     TEST_ID="Test setting $unit brightness to $bri"
 
-    expect_pattern `eval echo $index` $bri
+    expect_pattern $(eval echo $index) $bri
 
     $X52CLI bri $unit $bri
 

tests/libx52/test_indicator

@@ -17,7 +17,7 @@ indicator_test()
     local value="\$X52_INDICATOR_STATE_${state}"
     TEST_ID="Test setting $indicator $state"
 
-    expect_pattern `eval echo $index $value`
+    expect_pattern $(eval echo $index $value)
 
     $X52CLI $indicator $state