Fix CmdShowInterfaceTrafficTestFixture when stdout is a terminal

[benoit-nexthop]

Description

Fix CmdShowInterfaceTrafficTestFixture so it passes when stdout is a terminal.

Motivation

The code was mishandling when to add colors to the output in a way that
made the test fail when stdout was a terminal:

$ /var/FBOSS/tmp_bld_dir/build/fboss/fboss2_cmd_test 
--gtest_filter=CmdShowInterfaceTrafficTestFixture.printOutput
Note: Google Test filter = 
CmdShowInterfaceTrafficTestFixture.printOutput [==========] Running 1 
test from 1 test suite. [----------] Global test environment set-up. 
[----------] 1 test from CmdShowInterfaceTrafficTestFixture [ RUN      ]
CmdShowInterfaceTrafficTestFixture.printOutput ERRORS 1 interfaces, 
watch for any incrementing counters: 
/var/FBOSS/fboss/fboss/cli/fboss2/test/CmdShowInterfaceTrafficTest.cpp:186:
Failure Expected equality of these values:
  expectedOutput
    Which is: "ERRORS 1 interfaces, watch for any incrementing counters:\n Interface Name  Peer         Status  FCS  Align  Symbol  Rx   Runts  Giants  Tx  \n---------------------------------------------------------------------------------------------\n eth2/1/1        fsw002.p001  up      0    0      0       100  0      0       100 \n\n Interface Name  Peer         Intvl  InMbps    InPct  InKpps  OutMbps    OutPct  OutKpps \n---------------------------------------------------------------------------------------------------\n eth1/1/1        fsw001.p001  0:60   9876.54   9.88%  6.00    79012.35   79.01%  15.00   \n eth2/1/1        fsw002.p001  0:60   9876.54   4.94%  6.00    79012.35   39.51%  15.00   \n eth3/1/1        fsw003.p001  0:60   9876.54   2.47%  6.00    79012.35   19.75%  15.00   \n Total           --           --     29629.63  4.23%  18.00   237037.04  33.86%  45.00   \n\n"
  output
    Which is: " Interface Name  Peer         Status  FCS  Align  Symbol  Rx   Runts  Giants  Tx  \n---------------------------------------------------------------------------------------------\n eth2/1/1        fsw002.p001  up      0    0      0       100  0      0       100 \n\n Interface Name  Peer         Intvl  InMbps    InPct  InKpps  OutMbps    OutPct  OutKpps \n---------------------------------------------------------------------------------------------------\n eth1/1/1        fsw001.p001  0:60   9876.54   9.88%  6.00    79012.35   79.01%  15.00   \n eth2/1/1        fsw002.p001  0:60   9876.54   4.94%  6.00    79012.35   39.51%  15.00   \n eth3/1/1        fsw003.p001  0:60   9876.54   2.47%  6.00    79012.35   19.75%  15.00   \n Total           --           --     29629.63  4.23%  18.00   237037.04  33.86%  45.00   \n\n"
With diff:
@@ -1,3 @@
-ERRORS 1 interfaces, watch for any incrementing counters:
  Interface Name  Peer         Status  FCS  Align  Symbol  Rx   Runts  Giants  Tx  
 ---------------------------------------------------------------------------------------------

[  FAILED  ] CmdShowInterfaceTrafficTestFixture.printOutput (6 ms)
[----------] 1 test from CmdShowInterfaceTrafficTestFixture (6 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test suite ran. (6 ms total)
[  PASSED  ] 0 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] CmdShowInterfaceTrafficTestFixture.printOutput

 1 FAILED TEST

Whereas the test would pass if stdout wasn’t a terminal:

$ /var/FBOSS/tmp_bld_dir/build/fboss/fboss2_cmd_test --gtest_filter=CmdShowInterfaceTrafficTestFixture.printOutput | cat
Note: Google Test filter = CmdShowInterfaceTrafficTestFixture.printOutput
[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from CmdShowInterfaceTrafficTestFixture
[ RUN      ] CmdShowInterfaceTrafficTestFixture.printOutput
[       OK ] CmdShowInterfaceTrafficTestFixture.printOutput (6 ms)
[----------] 1 test from CmdShowInterfaceTrafficTestFixture (6 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test suite ran. (6 ms total)
[  PASSED  ] 1 test.

Also when using EXPECT_EQ() the expected value must come first. For
multi-line strings it makes a difference because the diff is printed in
reverse otherwise.

Test Plan

Existing unit tests pass.

[meta-codesync]

@joseph5wu has imported this pull request. If you are a Meta employee, you can view this in D85605968.

[facebook-github-bot]

@benoit-nexthop has updated the pull request. You must reimport the pull request before landing.

[meta-codesync]

@joseph5wu merged this pull request in 3868f77.