Test failure regression in nightly / beta

[jblondin]

Tests are failing sporadically in nightly and beta.

I've seen failures in the unique_single and unique_composite unit tests:

running 1 test
test view::tests::unique_single ... FAILED

failures:

---- view::tests::unique_single stdout ----
 EmpId | DeptId | EmpName 
-------+--------+---------
 0     | 1      | Sally 
 2     | 2      | Jamie 
 5     | 1      | Bob 
 6     | 1      | Cara 
 8     | 3      | Louis 
 9     | 4      | Louise 
 10    | 4      | Ann 

[0, 1, 5]
thread 'view::tests::unique_single' panicked at 'assertion failed: `(left == right)`
  left: `[0, 1, 5]`,
 right: `[0, 1, 4, 5]`', src/view.rs:2081:9sts::unique_single ... FAILED

failures:

---- view::tests::unique_single stdout ----
 EmpId | DeptId | EmpName 
-------+--------+---------
 0     | 1      | Sally 
 2     | 2      | Jamie 
 5     | 1      | Bob 
 6     | 1      | Cara 
 8     | 3      | Louis 
 9     | 4      | Louise 
 10    | 4      | Ann 

[0, 1, 5]
thread 'view::tests::unique_single' panicked at 'assertion failed: `(left == right)`
  left: `[0, 1, 5]`,
 right: `[0, 1, 4, 5]`', src/view.rs:2081:9
note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.


failures:
    view::tests::unique_single

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 43 filtered out

running 1 test
test view::tests::unique_composite ... FAILED

failures:

---- view::tests::unique_composite stdout ----
thread 'view::tests::unique_composite' panicked at 'assertion failed: `(left == right)`
  left: `[0, 2, 4, 5, 6]`,
 right: `[0, 1, 2, 4, 5, 6]`', src/view.rs:2107:9
note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.


failures:
    view::tests::unique_composite

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 43 filtered out

and the aggregate doctests:

running 2 tests
test src/view.rs - view::DataView<Labels, Frames>::aggregate (line 1396) ... ok
test src/view.rs - view::DataView<Labels, Frames>::aggregate (line 1434) ... FAILED

failures:

---- src/view.rs - view::DataView<Labels, Frames>::aggregate (line 1434) stdout ----
thread 'src/view.rs - view::DataView<Labels, Frames>::aggregate (line 1434)' panicked at 'test executable failed:
 EmpId | SalaryYear | Salary 
-------+------------+--------
 0     | Year2010   | 1500 
 0     | Year2011   | 1600 
 0     | Year2012   | 1700 
 0     | Year2013   | 1850 
 0     | Year2014   | 2000 
 1     | Year2010   | 900 
 1     | Year2011   | 920 
 1     | Year2012   | 940 
 1     | Year2013   | 940 
 1     | Year2014   | 970 
 2     | Year2010   | 600 
 2     | Year2011   | 800 
 2     | Year2012   | 900 
 2     | Year2013   | 1020 
 2     | Year2014   | 1100 


thread 'main' panicked at 'assertion failed: `(left == right)`
  left: `(4, 2)`,
 right: `(5, 2)`', src/view.rs:46:5
note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.

', src/librustdoc/test.rs:341:17
note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.


failures:
    src/view.rs - view::DataView<Labels, Frames>::aggregate (line 1434)

test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 6 filtered out

Test failures are sporadic. Sometimes all of the above tests will pass. Test failure has not been observed on stable.