Clean up code duplication in tests

While working on pr #299 I noticed that some test have quite a bit of duplicated code. E.g pattern like the following repeats quite a lot `"% fgrep "array_names" * | wc -l" -> 18`:

``` c++
vector array_names = { "data_array_a", "data_array_b", "data_array_c",
"data_array_d", "data_array_e" };
vector refs;
for (const auto &name : array_names) {
refs.push_back(block.createDataArray(name,
"reference",
DataType::Double,
{0}));
}
```

Start by reviewing the duplicated test pattern shown in the issue and use the `fgrep "array_names"` search to locate its occurrences. Inspect the related tests and PR #299 for context; done means consolidating repeated setup without changing test behavior, then running the affected test suite.

Written by the indexing model from the issue text.