date1<-as.Date(c("1987-01-01", "1987-01-02",
                "1987-01-03","1987-01-04","1987-01-05"))
date2<-as.Date(c("1987-12-30","1987-12-31","1988-01-01","1988-01-02"))

test_that("yrfraction works", {
  expect_equal(yrfraction(date1), c(0,1/365,2/365,3/365,4/365))
  expect_equal(yrfraction(date2), c(363/365,364/365,0,1/366))
  expect_equal(yrfraction(c(1,2,3),type="weekly"), c(0,1/(365.25/7),2/(365.25/7)))
  expect_equal(yrfraction(c(1,2,3),type="monthly"),c(0,1/12,1/6))
})
## same logic as inverse year fraction. 
## takes readily identifiable dates and tests in yrfrac correctly maps them.