Capture and record database transactions and save them as mocks

When creating database fixtures, it can sometimes be helpful to record the responses from the database for use in crafting tests.

Usage

start_db_capturing(path, redact_columns = NULL)

stop_db_capturing()

capture_db_requests(expr, path, redact_columns = NULL)

Arguments

path: the path to record mocks (default if missing: the first path in db_mock_paths().
redact_columns: a character vector of columns to redact. Any column that matches an entry will be redacted with a standard value for the column type (e.g. characters will be replaced with "[redacted]")
expr: an expression to evaluate while capturing requests (for capture_db_requests())

Value

NULL (invisibily)

Details

You can start capturing with start_db_capturing() and end it with stop_db_capturing(). All queries run against a database will be executed like normal, but their responses will be saved to the mock path given, so that if you use the same queries later inside of a with_mock_db block, the database functions will return as if they had been run against the database.

Alternatively, you can wrap the code that you are trying to capture in the function capture_db_requests({...}) this does the same thing as start_db_capturing() and stop_db_capturing() but without needing to remember to stop the recording.

You can redact certain columns using the redact_columns argument. This will replace the values in the column with a generic redacted version. This works by always passing the data being saved through redact_columns.

note You should always call DBI::dbConnect inside of the capturing block. When you connect to the database, dittodb sets up the mocks for the specific database you're connecting to when you call DBI::dbConnect.

Examples

# \donttest{
if (check_for_pkg("RSQLite", message)) {
  # Temporary files for examples
  nycflights_path <- tempfile()

  con <- nycflights13_create_sqlite(location = nycflights_path)
  dbDisconnect(con)

  start_db_capturing()
  con <- dbConnect(RSQLite::SQLite(), nycflights_path)

  df_1 <- dbGetQuery(con, "SELECT * FROM airlines LIMIT 1")
  res <- dbSendQuery(con, "SELECT * FROM airlines LIMIT 2")
  df_2 <- dbFetch(res)
  dbClearResult(res)

  dbDisconnect(con)
  stop_db_capturing()

  start_db_capturing(redact_columns = "carrier")
  con <- dbConnect(RSQLite::SQLite(), nycflights_path)

  df_3 <- dbGetQuery(con, "SELECT * FROM airlines LIMIT 3")

  dbDisconnect(con)
  stop_db_capturing()

  with_mock_db({
    con <- dbConnect(RSQLite::SQLite(), nycflights_path)

    # the result from df1 above
    print(dbGetQuery(con, "SELECT * FROM airlines LIMIT 1"))

    # the result from df3 above
    print(dbGetQuery(con, "SELECT * FROM airlines LIMIT 3"))
  })
}
#> Creating the testing database from nycflights13
#> Creating table: airlines
#> Creating table: airports
#> Creating table: flights
#> Creating table: planes
#> Creating table: weather
#>   carrier              name
#> 1      9E Endeavor Air Inc.
#>      carrier                   name
#> 1 [redacted]      Endeavor Air Inc.
#> 2 [redacted] American Airlines Inc.
#> 3 [redacted]   Alaska Airlines Inc.
#>      carrier                   name
#> 1 [redacted]      Endeavor Air Inc.
#> 2 [redacted] American Airlines Inc.
#> 3 [redacted]   Alaska Airlines Inc.
# }